Hello, glad to be among you!)
Used external connections to the asset directory,
initially used port 389 for connection after studying the connection manual LDAP — Dovecot documentation
The solution to the problem was when I stopped using port 389 and started using port 3268, after that the problem with connecting and displaying mailboxes went away.
The first installation without migrations was carried out according to the manual:
https://docs.nethserver.org/projects/ns8/en/latest/install.html