Landing within the X.Org Server Git code-base is partial xvidmode extension support for XWayland, for running older Linux games that lack native Wayland support, such as those making use of SDL1. The work was done by Red Hat's Olivier Fourdan.
Xvidmode is an old extension for getting the available X video modes. This basic implementation is limited and read-only but apparentlyu good enough for getting some older games running that rely upon this X11 extension.
Details via this Git commit. This XWayland gaming improvement will be found in the X.Org Server 1.19 release due out later this year.