This happened to me recently also. I had to disable my iGPU because Diablo 4 wouldn’t even launch. But Diablo 3 always launched and ran just fine. Now when I launch Diablo 4 it says “GPU not supported” but the game launches and runs fine. During my trouble shooting problem I switched from Lutris/Wine to Steam/Proton and I had the same problem. It’s interesting to see someone else encounter the issue as well.

Gardens of the Moon by Steven Erikson