Nextcloud 17 and user_ldap

I have a question regarding some issues with my nextcloud installation after upgrade from 15.0.4 to 16.0.8 to 17.0.0
I started with upgrading my existing and well running instance 15.0.4 to a newer version. After the upgrade all my users stored in an existing ldap directory are now lost, or nextcloud is not able to show it. In the Logging I only see tons of messages

TypeError: Argument 1 passed to OCA\User_LDAP\Group_LDAP::walkNestedGroups() must be of the type string, null given, called in /var/www/nextcloud_17.0.0/apps/user_ldap/lib/Group_LDAP.php on line 796

but if a look into the users config, no user is there. When I go to the ldap config, everything looks fine. nextcloud is able to connect to the ldap server and is able to find all users.

In a older thread I found a way to replace the whole user_ldap dir by an version fro 15.0.4 and indeed it works. After changing the version id in the info.xml file, I’m able to see all my users and they can login and work. But the error tables is flodded with messages like

InvalidArgumentException: Notifier LDAP Benutzer- und Gruppen-Backend (id: user_ldap) is not considered because it is using the old way to register.

I don’t know where my problem is and why it is not working. Maybe there is a better workarround to use my ldap users again.

For this error, I found something in the bugtracker:

If this does not help and an update like this breaks your setup, consider opening a bug report at github.