One of the Heroic devs is working on project Xodus, which is aiming to make game pass and other windows store games work on Linux/steam deck. They already have Xbox logins, license checks, and game downloads working, but are still working on the games themselves.
An important note:
That being said, the Xodus project is targeting games using Microsoft’s newer GDK and MSIXVC format. Older apps that use the UWP format, such as many games released during the Windows 8 and early Windows 10 period (Forza Horizon 3, Gears of War 4), aren’t planned to be supported.
UWP may get support eventually, but not anytime soon. They’ll have to get other stuff working first