There is a bug where the unity hub will not allow 2 projects with the same base name to exist in the list.
I have a Project Directory with a bunch of different folders, each named for a unity version. Part of development sometimes involves copying a unity project and updating it to use a newer unity version. If I attempt to manually open the copied project it will delete the previous one from the unity hub Projects list even though the path and the unity version are different.
Fixing this issue would make unity Hub very useful. A nice bonus feature would be if the hub could automatically clone a selected project and open it in a newer version of unity.