Very strange issue. On my desktop and laptop, same system Ubuntu 20.04.1LTS. I use the desktop to test the new system and software release and my laptop for imaging.
Since Kstars V3.5, my QHY183C cannot connect with the message "No QHY cameras detected. Power on?" on the desktop but not on the laptop !
It is a software, AstroDMXCapture, a french planetary imager, that modifies the 85-qhyccd.rules. So I copy this file from my laptop to my desktop and everything is in order.
This software replaces lines of the 85-qhyccd.rules, installed by Kstars or Indi (?), by his own rules.
And so you cannot connect the camera with these rules, into Ekos.