No wayland since 20210920

Hi, wayland/plasma doesn't start any more after on my venerable HD5450 since 20210920. It freezes immediately after startup with a black screen and a static mouse pointer. VT switching doesn't work. Recovery via SysRq-e is possible. It's reproducible: Wayland works again after rolling back; re-installation of > 3000 packages results in wayland freezing. Both IceWM and plasma on X11 are working. Is anybody else experiencing such a problem with wayland? I can't find any error messages. Is there a possibility to enable extra logging at startup of wayland or plasmashell? Thanks Bernhard