Contact groups can not be added to circles

Nextcloud version (eg, 20.0.5): 25.0.1
Operating system and version (eg, Ubuntu 20.04): Via Docker on Debian 11.5
Apache or nginx version (eg, Apache 2.4.25): Apache/2.4.54 (Debian)
PHP version (eg, 7.4): 8.1.13
Is this the first time you’ve seen this error? Y, first time I tried

The issue you are facing:
I am not able to add contact groups to circles. When I add a circle I interpret the description like that, that I can share contact groups with a circle:

Reason for that is, that I want to share a part of my address book (e.g. family) with my wife, which also is an Nextcloud user. Other contacts (e.g. her or my workmates) shall be available only in her or my address book. The contacts are not necessarily Nextcloud users.

I managed to create groups and assign contacts to them and I managed to create circles and to assign my wife and me as a user of the circle. But I did not manage to add contact groups to that circle.

Unfortunately the Nextcloud User Manual doesn’t describe circles in the contacts app.

Do I miss a button to add groups to circles anywhere or do I misunderstand the concept?

Thanks in advance for your reply!