Thanks for your help @ByteThis . I tried for about 3 hours yesterday and simply couldn't get it to work. I have decided to abandon the Powerblock and build my own from scratch. thanks agin for you help. regards Cliff
@Sailing_Nut You will have to use the older ubuntu distro for now I think. There's no-one really maintaining the ODroid compatibility (apart from me when I get the time and connect mine up).
Also there are issues with the packaged drivers conflicting with Debian packages - this is the fault of the distro.
(Or alternatively use another emulation distro for your board)
I found the 20.04 image and got RetroPie installed. Still working to see if I can get a game to run.