The samba TLS decryption errors can be ignored, see also After NETH8 migration - SAMBA shares on Windows cannot be accessed via the usual domain name - #9 by davidep
As a workaround you could filter those messages from being written to messages log, there were similar issues with SOGo in NS7, see also SOGo — NethServer 7 Final
The smb.conf for instance samba1 is located in /home/samba1/.local/share/containers/storage/volumes/config/_data/smb.conf