I have been running Raspberry PI 4 with Kstars 3.5.5 and indilib 1.9.2 with the same problem. I installed Kstars 3.5.6 and indilib 1.9.3 from sources. Still the same problem.
However, it works on my PC/laptop running Kubuntu 20.04, also on Opensuse Leap 15.3, so it seems to be an environment problem.
I ended up installing Ubuntu Mate on the RPI 4 with the latest Kstars/indilib from repositories, and now it works.

So that may be the quickest/easiest solution for you?

++Håkan W++