stefan It would be nice to have this info as part of the system requirements on the official docs though.
This way is a little hard to find.
For example, complete list of ports to open in external firewall:
22/tcp # for SSH
80/tcp # for HTTP websites via Nginx
53 # for DNS services using Named service
443/tcp # for HTTPS websites via Nginx
2083/tcp # as the default port for OpenPanel
2087/tcp # as the default port for OpenAdmin
32768:60999 # Docker range
I forgot to open them before doing an ARM test.