How to determine who the Owner of a Yahoo Group is?

Answer 1

You can't. Yahoo Groups to shut down on December 15, 2020: https://help.yahoo.com/kb/SLN35505.html

Answer 2

well, you could send them an email.

if the groups is [e-mail], you send your message to [e-mail]

Answer 3

It's pointless. Verizon  TERMINATED access  to ALL the Yahoo neo Groups on October 15. They will ALL he deleted or archived on December 15. This?was a decision made by VERIZON,

NOT Yahoo.  Verizon OWNS Yahoo. The moderator of a Yahoo neo Group was NOT the owner of it.