Probably Manjaro KDE.
Even Valve recommends it.
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If you care about VRR or HDR, you need a distro with KDE Plasma and use a Wayland session. Plus, you'll need the latest drivers, so... a rolling release.
Arch based like Manjaro, or OpenSUSE.
If you don't like that, or you have an NVIDIA GPU then I suggest you try Nobara, made by Glorious Eggroll, big contributor to Proton (Valve's fork of Wine, what makes Windows games run on Linux).
@stephfinitely If you want a GNU/Linux distro that is set up for gaming out of the box, you could try out Nobara (Fedora based), it comes with a lot of tweaks out of the box (the Linux Zen kernel for example).
Garuda or endeavourOS