This is from a very quick test. My headtracker[1] is not really calibrated at all (moved the workstation) and it's a very aged version of OpenTrack (snap package) in use but I'm really happy that this works now at all.

The game is Fly Dangerous[2] (public beta branch, free game, opensource) played via Proton. In theory that works on the native one too but the public beta branch is not up to date enough to test it already.

[1] https://beko.famkos.net/2021/07/08/diy-headtracker-for-gaming-on-linux-pc/ [2] https://store.steampowered.com/app/1781750/Fly_Dangerous/