Tutorial Projects won't run (MacOS)

Unity 2018.3.12f1 on a i5-Mac: Tutorials just won’t start, no error-message from Unity - except “2D Game Kit” which says “look like there is error in the project and that shouldn’t happen on the first launch”, which sends me here.

MacOS has the following error:

nw_path_close_fd Failed to close guarded necp fd 21 [9: Bad file descriptor]

I’ve been developing a project for android, and recently switched targets to Mac OS X the project starts and gets stuck. It is running but all i see is the animated background which stays persistant (DoNotDestroy) before the main menu loads. But the main menu never loads, and in the Os Console is see:

nw_path_close_fd Failed to close guarded necp fd 95 [9: Bad file descriptor]