in case you want to connect for syncing your Nextcloud with a local LAN connection as well as out of your local LAN ( via duckDNS,spDYN,etc.), the following config adjusting works for me.
To enable a local connection, you have to forward the exposed Docker port 443 (80 if needed) to your wished port - here 444. The Nextcloud config needs little adjustment as well. Add your OMV IP with respective Nextcloud Docker port to the trusted_domain array.
Furthermore, when you follow the provided instructions on how to setup the linuxserver/letsencrypt, you have to add following lines to your Nextcloud config:
Here you have to change the 'overwrite.cli.url entry and delet or mark as comment overwritehost in the Nextcloud config:
Restart your Nextcloud Docker.
Now you should be able to open Nextcloud with your local IP as well with your own domain. But be aware, if you log in locally and share a folder/file, the created link will be with your local IP and therefore not accessible from outside of your network. You can either replace the IP from the created link with your domain
or you have to login with your domain on Nextcloud and create the share link from there.