Editing Nextcloud (section)

=== Changing port numbers ===

/var/snap/nextcloud/current/nextcloud/config/config.php

 sudo snap set nextcloud ports.http=81
 sudo snap set nextcloud ports.https=444
 sudo snap set nextcloud ports.http=81 ports.https=444

Note: Let's Encrypt will expect that Nextcloud is exposed on ports 80 and 443. If you change ports and don't put Nextcloud behind a proxy such that ports 80 and 443 are sent to Nextcloud for that domain name, Let's Encrypt will be unable to verify ownership of your domain and will not grant certificates.

Also note: Nextcloud's automatic hostname detection can fail when behind a proxy; you might notice it redirecting incorrectly. If this happens, override the automatic detection (including the port if necessary), e.g.:

 sudo nextcloud.occ config:system:set overwritehost --value="example.com:81"