This was fixed for me in the latest build of kstars 3.6.0.
I also tried a complete fresh re-install of Indi-full and kstars-bleeding, but the result is the same.
I get the same error with the kstars 3.6.0 release. Here is a screenshot of the log messages
Thank you everyone. The problem is fixed!
I attached an external USB3 hub to the RB4's USB3 port, and then passed all my USB through that hub. I can now access the CEM40 mount from within Ekos. Incidentally, I also discovered that this mount has a pre-installed iPolar, something I don't remember seeing when I bought it. But all the devices can be accessed now.
I'm not sure that this hub I am using is "powered" as there is not an external power supply attached. But perhaps the use of the USB3 port provides extra power.
I have a brand new iOptron CEM40EC and I am trying to get it to connect to one of my Stellarmates. I have tried all the cable and port combinations I can think of, including an RS232 to FTDI/USB, which works very well for my CEM120EC2.
Has anyone out there successfully made this connection? Note that the newer CEM40EC port configurations are different from what iOptron shows in the manual.