It seems to work as expected on updated machine.
On a clean one, you need a systemctl restart netdata.
I just added a fix, thank you for reporting! → update event: restart netdata by gsanchietti · Pull Request #63 · NethServer/nethserver-squid · GitHub
We are working to restore access on port 980, my dream broke apart 
Access web applications from port 980 · Issue #6344 · NethServer/dev · GitHub