Executing: kinit -p administrator samba-tool domain join samdom.example.dom DC -k yes --dns-backend=BIND9_DLZ --option='idmap_ldb:use rfc2307 = yes' --option="password hash userPassword schemes = CryptSHA256" succeeds and generates entries in binddir/dns/. However, dns.keytab file is placed into private/ directory instead of binddir/, which is where it belongs. Additionally, dns.keytab is owned by root.root and has 0700 permissions. It probably should be owned by named. Most Bind9 installations run the daemon as named.
To be more specific, in my case: private = /var/lib/samba/private binddir = /var/lib/samba/bind-dns
Joseph can you take a look at finishing the MR and finalising this?
This bug was referenced in samba master: ae5964be42459beed8c174b8e2dd4d4167623158 9f1e5637bc5fe51c56ad996dd881779e6ef3c0aa
Fixed in Samba 4.15.