The user name format changed from the traditional ns6 username format, to the sssd upstream default username@domain format. As we've seen here, this is an issue for everyone trying to log on the machine with samba or ssh, or even the server-manager: the @domain suffix is frequently omitted and nothing works as expected.
Moreover, when migrating from an existing ns6 environment, any network client is configured with the traditional username format, and for this reason it should be reconfigured
Luckily there's a workaround for this! My first experiments with, ssh, postfix, dovecot, ejabberd and webtop4 are encouraging!
The configuration seems compatible with ns6 and ns7 (OpenLDAP). The nethserver-dc module still requires testing.