Camilladsp with Behringer UMC1820 - how to access spdif input!

I am able to use the analogue outputs on the UMC1820 with camilladsp (on linux), but nothing seems to get through on either the electrical spdif or the optical toslink. Using an alsa loopback works fine to get audio to the UMC1820, but I really want to drive camilladsp with input from another computer, not the one running camilladsp.
The number of channels for analogue output also seems to vary, having worked with 8 channels, 10 channels and even 12 channels . Can't remember what the circumstances were at the time.
My current conclusion on this issue is that UMC1820 simply does not work properly with camilladsp / linux. Prior to this, I was using brutefir, mainly with other cards, but also with the UMC1820 - it fairs no better.
If someone could show me a config.yaml that will work to access the UMC1820 I would be very grateful. I have wasted literally weeks on trial and error tests.
None of these issues are helped by the complete lack of any detailed tutorials or instructions concerning any linux software. The instructions, such as they are, are always incomplete and seem to assume you are an expert in everything that the instructions do not cover.

Many thanks,