we have recently been made aware of the fact that there are some issues when using the default RDP settings to connect to Ubuntu 22.04 LTS via RDP.
In Royal TS, the default RDP connection settings have the color settings set to 24-bit. Unfortunately, the Ubuntu default RDP settings require 32-bit and the value will not be negotiated during the connection. The solution, in this case, is simple. Open the properties of your connection and change the color depth setting to "True Color (32 bit)" in the settings:
You can find more information on this topic here: https://askubuntu.com/questions/1426376/native-rdp-on-ubuntu-22-04-not-working