By sealing for future writes, we broke Wayland SHM support. It seems like the wayland library maps the SHM in read/write mode. This is visible through no display and an error message like this: wl_shm@7: error 2: failed mmap fd 43: Operation not permitted Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5684>