I don’t want to steal @KU2Y’s thunder but he hasn’t posted about this here yet and I think this community would be very interested.
At the AMSAT Symposium a few weeks back, Alan (@KU2Y) gave a presentation on the CubeSat Simulator he has worked on with Pat, N8PK.
It incorporates enough pieces to simulate a solar/battery powered cubesat that beacons telemetry data using a raspberry pi and an AX5043 board.
You can see his presentation about this on YouTube here (starting around 5:12:00).
Wiki and code for his project can be found at https://github.com/alanbjohnston/CubeSatSim/wiki
Alan, the pics I took of your sim aren’t worthy of posting so if you have some to share please do!