If you go to announcements, you’ll find a thread on one of the larger group departures. But aside from that, you gotta keep track of which groups left on your own.
The groups that left usualy have restricted uploads so nobody can upload to said group if they arent one of the permited members. So basicly if you have things to upload by XXX group check their page. If you cant upload to that group dont do it. Theyve also mostly marked their profiles as do not upload