Thanks for the bug report. The attached log seems to explain the problem perfectly:
[10185.511277] rpi4b gnome-shell[2551]: Failed to post KMS update: drmModeAddFB does not support format 'AR24' (0x34325241) [10185.547140] rpi4b gnome-shell[2551]: Page flip discarded: drmModeAddFB does not support format 'AR24' (0x34325241) [10185.547707] rpi4b gnome-shell[2551]: Failed to post KMS update: drmModeAddFB does not support format 'AR24' (0x34325241) [10185.548506] rpi4b gnome-shell[2551]: Page flip discarded: drmModeAddFB does not support format 'AR24' (0x34325241) [10185.549013] rpi4b gnome-shell[2551]: Failed to post KMS update: drmModeAddFB does not support format 'AR24' (0x34325241) [10185.549464] rpi4b gnome-shell[2551]: Page flip discarded: drmModeAddFB does not support format 'AR24' (0x34325241) [10185.558077] rpi4b gnome-shell[2551]: Failed to post KMS update: drmModeAddFB does not support format 'AR24' (0x34325241) ** Tags added: raspi raspi-gfx ** Package changed: gnome-shell (Ubuntu) => mutter (Ubuntu) ** Bug watch added: gitlab.gnome.org/GNOME/mutter/-/issues #2379 https://gitlab.gnome.org/GNOME/mutter/-/issues/2379 ** Also affects: mutter via https://gitlab.gnome.org/GNOME/mutter/-/issues/2379 Importance: Unknown Status: Unknown ** Summary changed: - Constant short periodic loss of desktop + Constant short periodic loss of desktop [Failed to post KMS update: drmModeAddFB does not support format 'AR24' (0x34325241)] -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gnome-shell in Ubuntu. https://bugs.launchpad.net/bugs/1988859 Title: Constant short periodic loss of desktop [Failed to post KMS update: drmModeAddFB does not support format 'AR24' (0x34325241)] To manage notifications about this bug go to: https://bugs.launchpad.net/mutter/+bug/1988859/+subscriptions -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
