After a public testing period of only a few days, Valve has already pushed out Steam Play Proton 5.0-8 pulling in plenty of upgrades and fixes for the compatibility layer.
Halo 2 is out on Steam now and much like Halo: Combat Evolved Anniversary and Halo: Reach, the single-player works nicely on Linux thanks to the Proton compatibility layer for Steam Play.
Valve and CodeWeavers continuing the long task of improving the Proton compatibility layer (based on Wine) for Steam Play, and today a new Release Candidate went up for some testing.