OpenTrack is alright :) The trick is to get it to play nice with Proton. I’ve some scribbles ott here: https://simpit.dev/systems/opentrack/

I also was with the closed beta of the Linux native version of the Beam Eyetracker, which is kinda rad if you just have a webcam/smartphone cam and want to get some experience without investing into more expensive hardware. It utilizes the same mechanisms under the hood but comes with a fancy GUI and a setup wizard so that is really smooth sailing for newcomers.

Nothing stopping you from making your own tracker with cardboard and a bunch of IR LED tho. Been there :)

It really depends on the game. Sometimes I map it to a gamepad. In this particular example it’s using “TrackIR”, which is basically using memory mapping under the hood.