proton-standalone

run non-steam games with Proton and the Sniper runtime without messing everything up. it's called proton-standalone despite very much depending on Steam files by default, not hard to just throw those somewhere else and change the paths in proton-standalone.sh though. very easy to divorce Proton and Sniper from Steam and use them with proton-standalone without issue if you want to, not much of a reason to do so if Steam is already installed though.

you should probably just use umu unless you very particularly want the most minimal way of using Proton and Sniper with non-Steam games. expect this to not work down the line, will likely require you to change the "sniper_version" variable at some point in time. Don't use this unless you really want to use the exact version of Proton and Sniper runtime that Steam comes with to run non-Steam games.

you have been warned.