I have just managed to set up Z2M successfully after a long and frustrating session. The dongle was seen by HA in settings > system > hardware and that string copied and used in the serial section of the Z2M configuration. Onboarding repeatedly failed with refused to connect messages.
I checked the dongle firmware was ok. I confirmed the dongle worked by setting up ZHA and adding a zigbee device to the network. After deleting the ZHA instance I finally managed to get Z2M to onboard by installing Z2M edge. Added devices successfully in the normal way.
I’m guessing that the latest Z2M stable needs a tweak since edge works fine.
Anyone ( most users) smarter than me care to offer an opinion?