I KNOW steam supports it because it worked just fine when I had fractional scaling going under gnome alongside the experimental xwayland fractional scaling aware patches
meanwhile it's working perfectly under GNOME wayland with gnome's experimental fractional scaling enabled and an experimental xwayland fractional scaling aware patch merged into the system
right click steam in the applications menu and click "edit application" and put what i have in the environment variables section but change the number to 2