If you go to the client download page there is a link to a Debian version.
The current link is https://static2.askmrrobot.com/amrbeta/client/AskMrRobotClient-349-debian.8-x64.zip
I do not have experience with Raspberry Pi’s, but if all you need is a Debian release I would think these would work (maybe with some coercing to get a usable .Net core to support the client). Zoopercat posted some help a while ago here about getting an Ubuntu install working, but it might help in pointing you towards some useful packages and install tips.
If you get it up and running I would be interested to hear about your results. I’ve been thinking about getting into RPi’s sometime, but hadn’t found a project that excited me. If this works I might pick up a couple myself.