I'm also an Astroberry (2.0.3) user running on a rpi4. My devices are: eq6r pro mount, electronic focuser, qhy5-ii-l mono guide cam, and a dslr as the main image camera (planning to buy a mono QHY, but still deciding). My 4 usb ports are busy. Everything is working fine. It's true I have had some problems, and actually sometimes kstars crashes or experience some strange behaviour, but I can live with it. The solution is fantastic for remote imaging.
For now I will continue using this setup, and I recommend it.
Can anybody confirm, by the way, if actually two qhy cams work together at the same time flawlessly?