I have been following this thread, since I ran into the same problem. Here what I did tonight:
Compiled KStars from the latest github source (commit db1a82113a54b2e568ee4a259053b88d4473379e)
Left INDI at the last stable version (1.8.5) from the ppa
I then did a few "Capture & Solve" runs to different targets (Delta Cyg, M 13, M 57, M 27), and everything is working fine for now.
My system: Raspberry Pi 4 (4 GB) running Ubuntu 20.04 with Mate desktop. Log is attached.
Could this indicate that the issue may be with INDI rather than KStars?