Since nvidia drivers do not properly implement implicit sync, this protocol not existing is the root cause of flickering with nvidia graphics on Wayland. This MR being merged means that Wayland might finally be usable with nvidia graphics with the next driver release.
EDIT: Nvidia dev posted that support is planned in the 555 driver, with beta release planned for May 15: https://github.com/NVIDIA/egl-wayland/pull/104#issuecomment-2010292221
Does it have to be supported in wlroots/composers, or are these changes in wayland enough? Edit: nevermind, the pr links other prs, such as https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/4262
I saw a comment from an nvidia dev somewhere that XWayland support is enough to resolve the flickering, but compositor support is needed for best performance.