I don't know if this helps anyone but...
I successfully downgraded to 9.2 and can run Gateway! So, to help others along, I thought I'd share the sha1 hash of the zip file I used.
filename: 9.2.0-20U(Full).zip
sha1sum: ccc272c495a84aa49f8db2da6072a79a73053e19
Hopefully this helps people who are nervous if they grabbed the right file. Maybe we should make a pastebin/list of known hashes that work?
Thanks for the hash helped me in my confidence with finding this on that iso site..
I would like to point out however even though it is labeled 9.2.0-20(Full).zip and the hash was exactly the same when I did this process I was downgraded from 10.3 to 9.0.0-20
reading on the thread it was found on others appear to have this same problem as this was mislabeled and never fixed
I also would like to mention how I was able to increase the
success rate of loading sysUpdater for those still having troubles. It was not in this tutorial but perhaps can be added to the issues/resolution sections:
as per the github instructions load 3DS-FTP first (FTBRONY) then quicky close out of it by using L + R + B + Down on the DPAD, then quickly go to sysUpdater
So in more detail this is how I accomplished this:
1: Hold L to boot into homebrew via homemenuhax
2: Touch no buttons was for homebrew to load, quickly navigated down to FTBRONY and loaded that (By pressing on it via touch screen not pressing A, in case this alters anything too)
3: As soon as it loads I quickly HELD
L + R + B + DOWN
4: Again screen glitches as it will first Load homebrew as soon as I seen this I let go of all the keys and waited for it to fully load once more
5: Quickly Navigate to sysUpdater and load that (again, by pressing on it via touch screen not pressing A)
7: if all went well, you will see it load well pass step 5 (This is where I kept freezing via homemenuhax). I have had it freeze on step 7 and even just a little pass step 8. I notice that speed seem to improve my success rate and I was able to do this in 4 tries.
8: After it loaded I gave it about 30 seconds to be sure it wasn't doing anything else pressed Y to downgrade then waited for about 10 - 30 more seconds and it started to install the cia files.
So yeah hope this information helped! Thank you for providing this, I was waiting patiently to retire my O3DS Aqua blue so I could use my 3DSXL for this.