Outbound firewall rules:

HTTPS/443
UDP/53 – DNS
NTP/123 – NTP Time Sync

Also whitelisting the following URL's if your firewall is really restrictive about the network traffic.

*.rhombussystems.com
*.lan.rhombussystems.com
*.dash.rhombussystems.com

If you're using a firewall, you cannot man-in-the-middle (MITM) Rhombus network traffic as the cameras will detect this activity and stop the connection.

From https://support.rhombussystems.com/hc/en-us/articles/360008629411-What-ports-need-to-be-open-for-the-cameras-