Are they some graphic card benchmark for linux environment ? From my windows experience, drivers are important, and often underestimate. My linux gaming experience is very bad, lots of my game are unstable, and others use a lot more resources than with windows. However, when I ask people, some of them have no issue at all, even with a similar environment (Debian + Steam). I may consider buy specific graphic card to stay on linux, but I couldn't find any clue to know which one are more adapted.
Thx for your leads !
+1 for AMD, but...
This is misleading. OP may have chosen Debian for a reason, as most Debian users do, and they don't have to give it up just because they're gaming.
Even with Debian Stable and a very recent AMD card, they would just have to grab a newer kernel (the easiest would be from Stable Backports) and maybe new amdgpu firmware (from here). Everything else would be covered by the Steam runtime (or Flatpak, if they use that). It's not all that difficult. Performance is comparable to other distros.
Source: I game on Debian Stable with a recent AMD card.