Missing domain_name parameter in dhcp options while setting port dns names.
Upstream patch https://review.opendev.org/#/c/660423 provides this functionality. Unfortunately this can't be cherry-picked to Stein, because upstream Stein gates are configured to check against older version that OVS 2.12 (which is in fact not yet released).
For our downstream we can do this, because we have cherry-picked needed patch ourselves and its included in ovn2.11-2.11.0-26.el8fdp.
Related with my doubts from comment 3, this was already investigated here  and concluded that dns-name values from input parameters are ignored unless external_dns_driver = designate
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.