hi @ncwarrior
I was fighting the same problem few day ago. I forwarded my NC dns record cloud.mydomain.xyz to myfritz external DNS name. This resulted in DNS names resolved to the public IP of Fritzbox, so “somehow” Firefox and especially Nextcould apps on Android phones where failing to login as they hit Fritzbox login page…(=cert issue) I added Rebind protection for my cloud DNS and Myfritz address to the FB config without success.
The problem was not easy to solve - there are 3 parts of the solution:
- setup/use local DNS server like Pihole to create “split-brain” DNS for your Nextcloud installation
- define a local IP address for your Nextcloud instance DNS record
- BLOCK your myfritz DNS record (this is because clients, especially Android request both A=IPv4 and AAAA=IPv6 DNS records) - which results in public DNS request, so you get both you local IPv4 AND public IPv6 address, which heads to Firtbo login page
best regards, feel free to reach out if you have any questions