A Unity ID allows you to buy and/or subscribe to Unity products and services, shop in the Asset Store and participate in the Unity community.
Separate names with a comma.
Didn't work directly for me but I checked the log files (Top left menu > Troubleshooting > Open log folder -> cat info-log.json | grep Error) and...
I managed to make it work on on Linux (Ubuntu 20.04) with Unity Hub 3.1.2 ! You can access the log file at Top left menu > Troubleshooting > Open...