Valve put up a Release Candidate for testing Proton 10.0-4, what will become the main version of the Windows compatibility layer for Linux / SteamOS. The special sauce that enables so many thousands of games to run nicely.
Most of the changes would have already been in Proton Experimental. To test it out you can opt into the Beta on Proton 10 directly in your Steam Library. Valve are interested in finding any issues that didn’t happen with the current Proton 10.0-3.
I love how the “now playable” games listed in these fixes get more and more obscure. Just means that the well known games all work already