A small update: Syslog is flooded with messages like this:
2023-01-06T00:56:11.901415+01:00 waterhole plasmashell[3567]: [3604:3604:0106/005611.901154:ERROR:shared_image_factory.cc(575)] Could not find SharedIm ageBackingFactory with params: usage: Gles2|Raster|DisplayRead|Scanout, format: RG_88, share_between_threads: 0, gmb_type: shared_memory One every few seconds