Here began the problem in interaction with fusiondirectory and I
think
I understood now why:
The User Private Groups are implemented in debops in a very special
way
I think. (I don't know how common it is - I haven't found much about.
ok, you describe it here:
https://docs.debops.org/en/master/ansible/rol
es/slapd/ldap-schema.html#the-posixgroupid-schema - I should have read
it more carefully ;-)