3ds.guide it's all there

 

It includes all firmwares between 9 to 11.3. So Soundhax works for 11.2 too.

 

I recommend you to make a 9.2 emunand first:
1.Use soundhax to access homebrew launcher.
2.Unlink your Nintendo Network ID if you have it, go here:
https://3ds.guide/troubleshooting
scroll down to "Removing an NNID without formatting your device", but use homebrew launcher to go to "GodMode9".
3.Create emuNAND DON'T update to 11.4 at the end:

Then make A9LH:
https://3ds.guide/homebrew-launcher-(soundhax)
Use 3DNUS to download 11.2:
https://github.com/zoltx23/3DNUS/releases
just tape "11.2.0-35U" (I assume you got the USA version), and begin download.
go to emuNAND 9.2 install a CIA file with FBI of:
https://github.com/profi200/sysUpdater/releases
or
https://github.com/Plailect/sysDowngrader/releases (I recommend this one)
and update to 11.2 in emuNAND.
Then use "ctr-httpwn" with homebrew launcher in emuNAND:
https://github.com/yellows8/ctr-httpwn/releases
remember after you press START to exit press START again in homebrew launcher, and X to go back to the emuNAND HOME menu.
And go to System Settings to Sign back to your Nintendo Network ID. (use ctr-httpwn first if you want to go to any application that tells you to update to the latest firmware version, and online play).
Use Decrypt9 and make a sysNAND and emuNAND backup, or:
https://gbatemp.net/threads/emunand-tool-release-and-support-thread.359239/
for emuNAND backup.