[2020] Launching the game failed. [Linux]

Yes, can we see the error please?  

LocutusvonBorg said: trying to launch the stellaris.exe directly resulted in an error which says a d3d9_43.dll or something like that is missing. this is odd, cause i looked, i havent deinstalled anything related to that or installed something. and if its missing for 2.8.1, why isnt it missing for 2.1.x ?

Because 2.1. did not need that later DirectX 9 module but 2.8 does.

Please go here:
.../Steam/steamapps/common/steamworks Shared/_CommonRedist/DirectX/Jun2010/ and run dxsetup.exe from there.