User based external storage to owncloud

Hi all,
I ran Owncloud for a long time but now start the migration to Nextcloud.
Because of the underlying OS needs to be updated, too, this is not an inplace upgrade, but a migration.
I have setup an Ubuntu 18 Server with MariaDB 10.8, php 7.4 and Nextcloud 24
So far all is up and running.
To migrate the files I currently use raw SCP, but I wanted to fiddle around with “external storage”.
So I enabled the app and added a global external storage type webdav and pointed to my owncloud server. As authentication I selected “user entered, stored in database”.
Expected behavior: Any user has a folder “owncloud” in his file listing and if he/she clicks it, a prompt for credentials pops up on the first time.
After successful authentication the remote folder should be displayed.
Current behavior:
The user does have a folder named “owncloud” in his file list and is prompted for credentials.
But after this nothing happens.
In the nextcloud log it is written “empty response from server”.
I assume, I entered some wrong stuff in the global settings interface, but I am not able to find a correct how to, where owncloud connections are explained.
So my first question is, what do I need to enter exactly in the fields for URL?
My Owncloud server is bound to the FQDN: “https://owncloud.myinternaldomain.local
The webdav connection would extend that to “/remote.php/webdav”.
But neither the Base URL alone, nor the combination to the webdav URL do work.

What am I doing wrong?
br
Carsten

First i think this is not a good setting. Why do you not use Ubuntu 20.04 LTS or Ubuntu 22.04 LTS? Then you would not need a third party source for PHP and dist-upgrades not the next years.

To your question:
I do not really like External Storage and it does not work well. That is the truth. And WebDAV is bad, too.

You can better copy all files from Owncloud to Nextcloud e.g. with “scp” in the correct folders of the users (/path/to/nextcloud/username/files) and then.

sudo -u www-data php occ files:scan username
or
sudo -u www-data php occ files:scan --all

documentation

Additional hint:
By the way, i would not copy the trash can, for example. I would then also inform the users of this.

So just for the fun: Anybody out there, who has successfully connected a Nextcloud instance using external Storage with an Owncloud server?

Ok. But why does each user not use Federation? I think this is possible between Nextcloud and Owncloud and a nice feature also based on WebDAV.

Federation

WebDAV Nextcloud: https://cloud.server.tld/remote.php/dav/files/username/
Maybe same at Owncloud, but only “webdav” instead of “dav”. Sorry i do not use Owncloud.