Configure the desktop client

Dear all,

I finally got around to setting up my Nextcloud server. It runs on a Debian 10 server with Apache2, php7.3, mysql over a https connection. All error codes dealt with and redis deployed for smooth operation.

Now I installed the desktop client on my linux mint laptop but I never get to the server address. The client keeps bugging me to sign up for a free account with a provider.
Did I miss a step? How can I connect it to my own server?

Nextcloud server =
Nextcloud desktop sync = 2.6.2 (default on mint 20)