Dockerfile (and compose) for 3CX
https://www.3cx.com/community/threads/3cx-inside-docker-container.52232/
https://hub.docker.com/r/farfui/3cx
https://github.com/xrowgmbh/docker-3cx/blob/master/Dockerfile
https://hub.docker.com/r/jrei/systemd-debian/dockerfile
https://github.com/alexdzyoba/docker-debian-systemd/blob/master/Dockerfile
https://www.3cx.com/docs/manual/installation-linux/
https://www.3cx.com/docs/manual/configuring-your-pbx/
https://www.3cx.com/docs/ports/
https://www.3cx.com/docs/manual/firewall-router-configuration/