Don't use the native binary, it doesn't work well with mods. I'm on Pop OS.

Install the game with Proton 6.3 something or other (force compability in steam options for warband)

Manually install mod into your regular module folder

Select directx 7 in video options or the game will just not start loading

Go into the module.ini for the mod and look for a setting that says directx 7. Change from 0 to 1

And you're done.