Overrides for Steam/Proton

$ sudo getsebool selinuxuser_execmod

If this returns selinuxuser_execmod --> disabled you will need to enable the boolean.

This can be done on a temporary basis (only survives until next boot), with:

$ sudo setsebool selinuxuser_execmod 1

Or persistently with:

$ sudo setsebool -P selinuxuser_execmod 1

Setting this boolean does have potential security implications, but they are relatively minor. The safest way to do this, if you wish to use steam is to toggle this boolean on and off as necessary.