Firmware Update fails -> missing domain

When trying to update the Firmware of APs and switches, it always fails.
All domains mentioned in Nebula (https://nebula.zyxel.com/cc/ui/index.html#/help/firewall-information) are opened but it tried to connect to some different addresses.

I figured out, for updating the firmare, another (sub)domain is being requested:
firmware.nebula.zyxel.com on port 443

The corresponding IP-Adresses (as of 21.04.2022) are:

• 13.224.99.12
• 13.224.99.55
  
• 13.224.99.127
  
• 13.224.99.111
  

I do not know if they are dynamic or static, but would be glad if the domain (and IPs) can be added to the list on the mentioned link above.

Hopefully this helps if anybody else has the same problem and I'm looking forward to the domain being added.