Simplest way would be to open a term windows and type ‘ps aux | grep Xorg’ minus the quotes and hit enter. Ignore the output that has grep on it. Examine the output. If only one line, then you are most likely on wayland. There are other ways, but we would need to know more about your system.

What cards and wayland compositors/xorg are you using? I have a 4080 and am on plasma 6.3 and don’t have any graphical glitches with steam.

Yeah. Go into the system settings app, Autofill and Passwords. Select only the “AUTOFILL FROM” for Firefox.

Did you set Firefox as the default iPhone password manager?

Does hyprland support explicit sync at all? That sounds like the explicit sync issue that was fixed earlier this year.

Edit: Could run waycheck and see if linux-drm-syncobj-v1 (explict sync) is listed. I looked for NixOS and it “should” be supported, but best to double check.