>I don't know much about SQL Server and MySQL but I wouldn't favor a lockin closed source software or anything remotely connected to Oracle.

If that's a concern, then MariaDB is another alternative. Postgres isn't the only option in town.

EDIT: I'm correcting myself here because as far as I can tell, LISTEN NOTIFY equivalent capabilities are only available in MariaDB's SkyQL fully managed services offering, and not in the base MariaDB Community Server.