Most important thing was to have Apache listen on ports 591 for http and 4433 for https. Tomcat uses 8080, and either BigBlueButton or Nginx or Tomcat clashed with 8443.
Also my router didn't allow ports that were needed, nor did the Linux firewall under Virtualmin.
- TCP ports 80, 443, 1935, and 7443
- UDP ports in the range 16384 - 32768