If you can use the browser, I suggest that you use the new browserhax (up to 11.0.0-33!) in the meantime.

Try out Ubuntu 15.04: http://old-releases.ubuntu.com/releases/15.04/

This requires a New 3DS. The demo version doesn't work and is patched. If you have 1.1.3 or newer delete/disable the update data.
officially called smashbroshax sometimes smashax
Here is a new tool I call smashbroshax-helper. It is a graphical interface for the exploit which simplifies most of the process of broadcasting the packet. It requires almost no setup outside of creating a bootable Linux USB/DVD.

Important notes:

• This does not work on Fedora or Red Hat-based distributions because aircrack-ng needs to be compiled on it (and I can't figure out how to install the needed things).
  
• Don't use a virtual machine!
• This probably will never work on Old 3DS.

Download smashbroshax-helper beta

It is recommended that you use a live Ubuntu 15.04 image. Versions 15.10+ have issues. http://old-releases.ubuntu.com/releases/15.04/

1. Create a bootable USB/DVD with a Linux distribution (there are various guides online).
2. If possible, get a second USB/SD card/storage device, download and save the above .zip to it.
   • Don't extract the contents of it to the USB device, as it might cause problems. Just save the .zip file to it.
   • If you can't do this, you'll have to connect to the Internet while in Linux to download it.
   • If using a bootable USB, make sure you can use two ports at a time. Don't take out the Linux USB while it is being used!
3. Restart your computer and run the bootable USB/DVD you created.
4. Extract the contents of the .zip to the Desktop.
5. Open the smashbroshax-helper folder and double click "smashbroshax.sh".
6. Follow the on-screen prompts.
7. If everything goes well, you should now have homebrew!

Video demonstration, from boot to shutdown:

from https://gbatemp.net/threads/tutorial-using-smashhax-with-linux.397194/page-9#post-5842512

---

If you would like the full tutorial, involving terminal usage and compiling:

Spoiler: Everything

To reverse the changes to your wireless interface and remove issues connecting to networks after, rebooting your system or changing it to "Managed" instead of "monitor" should fix it. How to do that is in the second to last section.

---

@Cydget made a script that condenses most of this into a script. I have not tried it myself yet but it seems to work for others.

Spoiler

So, I made a little script for this. If anybody wants it, then unzip this file and read the readme. And yes, I like to pipe things. http://www.mediafire.com/download/oulnubnzkk9g3i0/smashhaxEZ.zip

---

Requirements

• Any Linux distribution should do (this has only been tested with Debian-based distributions). Windows and OS X users should wait or find a method for now, sorry!
  • Please do not use Linux in a virtual machine, it likely won't give direct access to your wireless card. Dual boot or use a live USB/disk.
  • The recommended distro to use is Ubuntu 15.04 (link to Ubuntu MATE 15.04).
• A Wi-Fi-capable wireless card.
• Super Smash Bros. for Nintendo 3DS Full or Demo.
• New 3DS. This does not work on Old 3DS.
• Patience. The hax is sort-of unreliable so your game will most likely crash a few times.
• Recommended: Another device to access the internet (phone, tablet, computer, console).

Preparing

• Install these packages using your package manager. For example, "apt-get" for Debian-based distributions (including Ubuntu).

  openssl libssl-dev libnl-genl-3-200 libnl-genl-3-dev libnl-3-200 libnl-3-dev pkg-config

• Find your wireless card's interface by opening a terminal and using the command "ip link". It would be something like wlan0 or wlp3s0.

  ian@ian-VPCEG34FX:~/Desktop/aircrack-ng-1.2-rc2/src$ ip link
  1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default 
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
  2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN mode DEFAULT group default qlen 1000
      link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
  3: wlan0: <NO-CARRIER,BROADCAST,ALLMULTI,PROMISC,NOTRAILERS,UP,LOWER_UP> mtu 1500 qdisc mq state DORMANT mode DORMANT group default qlen 1000
      link/ieee802.11/radiotap xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff

• You probably already have it, but get the homebrew starter kit and place it on your SD card.
• Download the smashhax .pcap files from the releases section of the smashbroshax repository.
• Determine the .pcap file to use. This should be straightforward using the file names.

  The built beacon-hax pcaps are located under "pcap_out/". In the filenames, "vXYZ" means game-version "vX.Y.Z". Full-game filenames for USA include "gameusa", while the other regions filenames include "gameother".

• Get the "Otherapp payload" from the Homebrew Launcher site and save it to "smashpayload.bin" at the root of your SD card.
  
• Download and extract aircrack-ng's latest release source.
• Save aireplay-ng.patch from the smashbroshax repository in the folder "aircrack-ng-1.2-rc2".

Compiling aircrack-ng/aireplay-ng

• Open a terminal and go to the "aircrack-ng-1.2-rc2" folder.
• Use the command "patch src/aireplay-ng.c < aireplay-ng.patch". If you get the following then it has succeeded.

  patching file src/aireplay-ng.c
  Hunk #1 succeeded at 560 (offset 1 line).
  Hunk #2 succeeded at 573 (offset 1 line).

• Run "make" and wait. The program should be compiled with the patch now. If you get the following as the last line then it has succeeded.

  make[1]: Leaving directory '/path/to/aircrack-ng-1.2-rc2/src'

The moment of truth

• Run these 3 terminal commands in order, using the wireless interface (from "ip link") you found earlier.
  
  sudo ifconfig wireless_interface down
  sudo iwconfig wireless_interface mode monitor
  sudo ifconfig wireless_interface up
  sudo iwconfig wireless_interface channel 6​
  (the last line was suggested by @difool. and might make the payload trigger faster)
• Enter the "src" folder in your terminal.
• Run the following command to start broadcasting the packet: "sudo ./aireplay-ng --interactive -r /path/to/smashbros_version_beaconhax.pcap -h 59:ee:3f:2a:37:e0 -x 10 wireless_interface"
  Use the .pcap file and wireless interface you found out earlier.
• On the 3DS system, start the game, then choose Smash and Group. Wait for the magic to happen.

Encountering errors? Something confusing?

• Does running aireplay-ng end with "End of file"? You might be running your installed version of aircrack-ng. Don't forget the ./ for "sudo ./aireplay-ng ..."!
• Please tell me the distribution you are using and the error you've encountered. This will help me fix your issue faster.
• If you don't get something, don't hesitate to point it out! I want to help anyone I can.
• Did you spot an inaccuracy or mistake I made? It would be great if you can tell me that too.
• This was before the Otherapp payload selector was added to the HBL site. This is kept here for legacy reasons or something.
  Spoiler

  • Determine what file you need to get from the Homebrew Launcher Payload section:
    
    Spoiler: Homebrew Launcher Payload

    With the release builds, the hax loads the payload from SD "/smashpayload.bin". This should contain the hb-launcher(https://smealum.github.io/3ds/) otherapp payload. Until there's a proper otherapp payload selector on the hb-launcher site, the payload can be downloaded from the following URL(see also https://github.com/smealum/sploit_installer):
    

    • "https://smealum.github.io/ninjhax2/Pvl9iD2Im5/otherapp/{PAYLOADNAME}.bin" Where {PAYLOADNAME} is: "FIRMVER_REGION_MENUVER_MSETVER".

    FIRMVER values(without quotes):
    

    • "POST5" = non-New3DS
    • "N3DS" = New3DS

    REGION values(without quotes):
    

    • "U" = USA
    • "E" = EUR
    • "J" = JPN

    MENUVER values(without quotes):
    

    • "11272": Non-JPN, system-version v9.0.
    • "12288": System-version v9.2.
    • "13330": System-version v9.3.
    • "14336": System-version v9.4.
    • "15360": System-version v9.5.
    • "16404": System-version v9.6.
    • "17415": System-version v9.7.
    • "20480_usa": USA, system-versions v9.9-v10.0.
    • "19456": Non-USA, system-versions v9.8-v10.0.

    MSETVER values(without quotes):
    

    • "8203": System-versions below v9.6.
    • "9221": System-versions starting with v9.6.

    For example, the payload URL for New3DS USA 9.9.0-X - 10.0.0-X is:https://smealum.github.io/ninjhax2/Pvl9iD2Im5/otherapp/N3DS_U_20480_usa_9221.bin
    The end result is a file named "smashpayload.bin" at the root of your SD card.

You are allowed to reproduce/reprint this tutorial, as long as a link back to this page (https://gbatemp.net/threads/tutorial-using-smashhax-with-linux.397194/) is included.

 

[Cydget]

So, I made a little script for this. If anybody wants it, then unzip this file and read the readme. And yes, I like to pipe things. http://www.mediafire.com/download/oulnubnzkk9g3i0/smashhaxEZ.zip

EDIT: Tutorial using this script is in a video lower on this page

 

[Lyomak]

When i type in the last command to start sending out the beacon it gives me this error in LXTerminal

sudo: ./aireplay-ng: command not found

Any idea what im doing wrong?

Check out this video, is in german but is pretty straight-forward. You can get the commands in the description also.

 

[Favna]

So, I made a little script for this. If anybody wants it, then unzip this file and read the readme. And yes, I like to pipe things. http://www.mediafire.com/download/oulnubnzkk9g3i0/smashhaxEZ.zip

I'll definitely look into this when I get my hands on a wifi stick.

 

[Cydget]

Thanks, it pretty much replaces doing all the things in the tutorial with two commands. You still need to download the payload tho

 

[Acryt]

Thanks, it pretty much replaces doing all the things in the tutorial with two commands. You still need to download the payload tho

Amazing, thank you. I just bought a N3DS XL that I have no idea what the firmware will be and might have to go back to smashhax.

 

[Cydget]

Automatically does all the package downloading and such?

The zip folder contains all the pcap files and the patched aircrack-ng. The rest is in the readme.txt file
I might make a video tutorial if people want it.

 

[ihaveahax]

So, I made a little script for this. If anybody wants it, then unzip this file and read the readme. And yes, I like to pipe things. http://www.mediafire.com/download/oulnubnzkk9g3i0/smashhaxEZ.zip

I'll test this out later, and add it to the post if it goes as intended.

 

[Acryt]

The zip folder contains all the pcap files and the patched aircrack-ng. The rest is in the readme.txt file
I might make a video tutorial if people want it.

I downloaded it to check what it was and saw Thank you for doing that. Makes my life easier since I didn't use a casper'd live boot.

 

[Favna]

The zip folder contains all the pcap files and the patched aircrack-ng. The rest is in the readme.txt file
I might make a video tutorial if people want it.

While I understand most of the process if not all, that video would still be much appreciated. It can never hurt, that's for sure !

 

[Cydget]

While I understand most of the process if not all, that video would still be much appreciated. It can never hurt, that's for sure !

So I made the video. I know its bad quality, but its my first one.

 

[Favna]

Well I guess this is some form of progress? It gets here pretty much instantly upon starting the group search - though also gets stuck here :\

Oh and my wifi usb crashes it's network upon reaching 93 packets -_-

I have the eurdemo infinite by the way

 

[ihaveahax]

Well I guess this is some form of progress? It gets here pretty much instantly upon starting the group search - though also gets stuck here :\

Do you have the correct otherapp payload at /smashpayload.bin?

 

[Favna]

Do you have the correct otherapp payload at /smashpayload.bin?

That's exactly what i'm going to double check now actually. Was rebooting and going to SD management while posting that.

 

[Cydget]

Well I guess this is some form of progress? It gets here pretty much instantly upon starting the group search - though also gets stuck here :\

Oh and my wifi usb crashes it's network upon reaching 93 packets -_-

I have the eurdemo infinite by the way

The demo doesent work well, and I think you might need a different wifi adapter

 

[Favna]

The demo doesent work well, and I think you might need a different wifi adapter

:\ aint got the full game and i sure as hell am not going to buy it just for smashhax LOL. But we'll see.. perhaps i just messed up on the payload.

--------------------- MERGED ---------------------------

Theoretically speaking, would it likely eventually work if i do get such a screen? (It actually kinda varies what kind of static it is). Seeing as how the demo doesn't work all that well, I figure perhaps if i keep on trying?

Edit:
Hmm... it looks more like it crashes when it starts picking up the packages on my n3ds. Odd... most odd.

Edit2:
What I said about different static screens:

 

[Cydget]

:\ aint got the full game and i sure as hell am not going to buy it just for smashhax LOL. But we'll see.. perhaps i just messed up on the payload.

--------------------- MERGED ---------------------------

Theoretically speaking, would it likely eventually work if i do get such a screen? (It actually kinda varies what kind of static it is). Seeing as how the demo doesn't work all that well, I figure perhaps if i keep on trying?

Edit:
Hmm... it looks more like it crashes when it starts picking up the packages on my n3ds. Odd... most odd.

Edit2:
What I said about different static screens:

Have you tried using the hax2 payload and boot.3dsx instead of the 2.5 one. I have a feeling that yellows8 only updated the retail game's pcap to work with hax2.5

 

[Favna]

Have you tried using the hax2 payload and boot.3dsx instead of the 2.5 one. I have a feeling that yellows8 only updated the retail game's pcap to work with hax2.5

I haven't, but I don't have them saved anymore either. Would you be able to supply them?

Edit: I mean the boot.3dsx at least. The payload is gonna be tougher... :\

 

[Cydget]

I haven't, but I don't have them saved anymore either. Would you be able to supply them?

Edit: I mean the boot.3dsx at least. The payload is gonna be tougher... :\

That should be the boot.3dsx from the day before hax2.5

 

[Favna]

Well lets try that then. I realized there is no *hax2.0 / *hax2.1 for the 10.2 payload since 10.2 came with 2.5 from the get-go. If just replacing the boot.3dsx doesn't work I guess I need to contact yellows8 (some way...) and confirm if the eurdemo was updated or not.

 

[Favna]

Well 30 mins later it still gives me the same result -sighs-

And I honestly don't even know how or where to contact yellows8 xD