MySQL 8.0.15 starts normally but any connection hangs
Everything but the bit about the general log was a distraction. Killing the mysqld daemon, disabling the general log in my.cnf and then restarting the server worked fine. Although I can't find this documented anywhere, apparently mysqld will be completely unresponsive while it is busy prowling through it's general log, and if that log is extremely large, it can take an arbitrarily long time.