Raspberry pi endpoint doesn't show up

Good to hear it. In that case then you should be able to download the Roon Bridge software and install it on that I think (using SSH), just as a test. Others here more expert on the Pi can give you the commands.

EDIT: instructions from your own thread first time round last year:

You do seem to have a fundamental SD card programming issue at the moment though. Can you program one with Raspian afresh and see if that works?