You must have set up a global environment variable for the HUD somewhere or set up a config file used by all games that enables it.
The first time I ever enabled this hud was in that launch option, so I am confident I did not create any such file.
If I am wrong, or a config file was created somewhere without me realizing, where would I find it?
Edit: to clarify, I have already investigated Steam's localconfig.vdf and user_settings.py files, and dxvk.conf does not currently exist.
If I am wrong, or a config file was created somewhere without me realizing, where would I find it?
DXVK doesn't create any config files on its own.
Just to rule that out: You're sure, what you're seeing is the DXVK HUD and not for example the Steam FPS counter?
You're sure, what you're seeing is the DXVK HUD and not for example the Steam FPS counter?
Absolutely. I can enable them both concurrently. Give me a moment and I can upload a screenshot.
Also if you can then share logs from a game. Then we can check if it's a config file it's picking up
Either way, this is 100% a user error and not a bug. DXVK never stores any environment variables or configuration persistently on its own.
Entering something like echo $DXVK_HUD in a terminal should reveal whether or not the env var is set globally. If that's not the case and you can't find the root cause, reboot the system I guess.
Here is a screenshot from Crusader Kings 2. As you can see both DXVK's hud and Steam's are visible in the upper corners.

echo $DVXK_HUD reveals, uh, nothing. Just a blank line. I have already rebooted several times.
Which game logs would contain the information you are looking for?
That is not the DXVK HUD, but the nvidia driver hud.
Well that's embarrassing. It turned on with the launch command I listed above. How do I turn it off?
Check the Nvidia X11 Settings.
Hey hey, it worked! Thanks for the help lol.
Problem Description
I enabled the DXVK fps hud via Steam launch options for ONE game through "DXVK_HUD=1 %fps%". The hud is now enabled in ALL of my games launched through Steam or Lutris, despite removing the launch option, and I can't find a way to disable it. Furthermore, I can't get it to display any different information - other launch options affecting the hud no longer work, nor does editing user_settings.py.
System
DXVK version 1.10.3
Lutris 0.5.12
Proton experimental-7.0-20230227
Drivers: Nvidia version 525.85.05