SteamOS is now officially on the list of Linux distributions Epic Games plans to support with its new Epic Games Launcher. In a statement to GamingOnLinux, Epic communications director Jake Jones said the launcher is still in Preview, and that Epic plans to "support as many Linux distributions as...
There’s another reason they’ve been encouraging devs to use Proton on Linux instead of a native build: you’re less likely to ship Linux-only bugs that can’t be replicated on Windows, which saves a ton of debugging (and maintaining a separate dev environment) to fix something a minority of players will ever encounter.
And those Linux-only bugs that do pop up are likely an issue with Proton itself, and Valve directly benefits when bugs in their product are reported.