Btw steredenn is even Linux natively, that's what made me even more angry.
That's basically the issue... especially older Linux ports run worse than the Windows version. I hope Valve will eventually consider setting Proton as the default for some games even when they are native, as their ports are usually abandoned and outdated.
Try switching it to launch the windows version through Proton instead of the Linux version. Loads of games work better that way I’ve found, since a lot of the Linux versions don’t get the same level of support.