So it's been about 2-weeks of using my PC after applying the fix posted above and quoted below and so far, there has been no further problems with RDP. I think this is a very annoying bug in the Microsoft code that they need to fix.
Specifically, I created a file named .wslconfig in the root folder of your Windows profile, like c:\users\loginname. In this text file add these 2-lines.
[wsl2] gui
Applications=false
Save the file and reboot. The focus theft stops.
Many thanks to the Dopus team for the help and research.