Tried both Stellaris and Moo2 with Proton 4.11 through current and with glorious eggroll version. No joy.
Stellaris does work with DirectX 9 renderer (running from proton), and DirectX 11 version requires using native d3dcompiler_47.dll (the game crashes with an assert when using a builtin version). After replacing the library it works correctly.
UPD: DirectX 11 version seems to consume much more gpu memory when compared to directX 9 renderer it seems.
Stellaris and Moo2 will not even start: No Launcher nothing just momentarily says running and then stops
KOTR II plays but no sound.
Ubuntu 21_10, 5.11..0 Kernel
RAM: 128Gb
I9 10 core
Nvidia GeForce RTX 2080 Super 3072 CUDA corees, 8Gb mem
optronics 4k display