The issue disappeared after I
compiled from source
over a fresh install of Ubuntu 22.04 headless server (no desktop) on an 8GB RPi4. Equipment was attached locally to the RPi4, and I ran kstars on the RPi4 with a remote X display (i.e., logged in to the RPi 4 via ssh -X from a remote X machine and ran kstars).
The
github issue page
(status now closed) says things should be cleaned up and fixed in the next release 2.0.8 due June 1, so this thread is now solved.