Use gamescope to run the game under Wayland. Gamescope creates an XWayland window (for which you can specify things like resolution, upscaling, and refresh rate) to run the game in, so the game can pretend it’s under X11, and gamescope interacts with Wayland.
Thanks, TIL
How is SteamOS on the Deck dealing with this? I thought they also used gamescope