Sorry for the delay, I had some problems with my code.
I guess this is why big companies have PR people, as developers tend to say things in a way which people don't understand.
Download this to your 3DS SDCard as /luma/sysmodules/TwlBg.cxi
Download this, install it on your 3DS, and follow these instructions to patch the kernel used in DSi mode:
open TWPatcher (purple Minecraft brick icon with Mario which says TWL in Comic Sans)
once opened, hold down Y, press B, and release Y, which should open the patch menu
hold down X, press A, release X, which should open a secret menu
instead of turning your 3DS off, hold START for a second, release START, wait a few seconds, and you should see "Disk write"
press B twice
hold SELECT to exit
Now boot a DS game which doesn't work for you, and either make a screenshot, or try to describe what text you can see on the bottom screen.
It's normal that the top screen is absolutely garbage, it's unfinished.
Once you're done screenshotting/writing down the values, hold SELECT to reboot.
The only "persistent" change is installing TWPatcher, which needs a bit of cleanup from SD and NAND(?) if you want to completely get rid of its traces (basically same cleanup procedure as any Title installed to SD). The rest are just files on the SD only, and you can revert it by deleting /luma/sysmodules/TwlBg.cxi and /luma/twl.firm