Is https://nextcloudpi.localdomain:4443 used for the admin panel?
I’ve never been able to log into it locally. What creds would I use, my admin account?
That isn’t a default port for Nextcloud.
Run the following command to get an idea which service is listening on that port:
# netstat -lnp | grep ":4443"
There is a different management page to configure other parts of the system:
https://pant.github.io/nextcloudpi-test-docs/en_How-to-access-and-activate-NextCloudPi.html