A new Wayland protocol is in the works that should support screen cutout information out of the box: https://phosh.mobi/posts/xdg-cutouts/ Hopefully this will be extended to include color information whenever applicable, so that "hiding" the screen cutout (by coloring the surrounding area deep black) can also be a standard feature and maybe even be active by default.
Wayland modularity is the gift that keeps on giving.