UPDATE: simply opening the exact same domain:8443 in a different browser, made the error magically disappear (again) upon which I could continue the installation.
Dear folks,
On OCI I have an instance of Ubuntu 24.04. On this I installed Docker Engine. On that I installed Nextcloud AIO via the standard script (so no reverse-proxy)
On the server where my domain runs, I made an A record called nc.domain.com which point to the public IP-address of OCI. It seems to work because if I go to the domain:8443 I see the Nextcloud AIO first intall page (with the passphrase).
I have opened tcp-ports 443, 8080 and 8443 and udp-port 443 (for https3)
However, on the page where I have to put in my domain, I get the standard DNS error. I already read about this problem, and sometimes it is “solved“ by merely waiting a bit.
I post this question because I ran into this ‘problem‘ before and it seems flaky to me. This was on Windows 10 with Docker Desktop with Nextcloud AIO on it. Sometimes it immidiately ‘got’ the domain, sometimes it kept nagging about ‘DNS config’ in the top-right corner. I even read about suggestions to cut out the domain-check from the docker install script.