Unless I am missing some obvious setting: Restricted Kubernetes doesnt work like that. You have to run the container with a non-root UID (usually something upwards of a million). Non-root users however can't reserve ports below 1025. Nextcloud builds on the default php-apache image which comes with the default apache ports.conf (Listen 80).

So now this has to be overwritten either by making a custom build (which may require creating a custom build pipeline) or by mounting a new config file (e.g. via ConfigMap) else it wont start. Both are an additional update risk which now has to be documented and checked before updating in addition to changes from the normal nextcloud changelog.

Similiar issues probably appear with rootless docker/podman unless you add extra capabilities, which is not possible in restricted kubernetes settings.