I've spent an entire day (20 hours) searching for a magic command to bring the GDM login manager back to life after upgrading #fc42 to #fc43. I'm not a novice. It would be difficult to make the answer harder to find. But it only took 1 command. Stuff like this is why the public is not embracing #Linux. I seriously considered scratching the entire installation and starting over. This is the worst #Fedora upgrade that I can remember, worse than upgrades involving ZFS, Nvidia, and Tuxedo drivers.