Since we are testing the PostgresPlusDialect on every commit against a EDBv14, I don’t think that there is anything significant missing right now. There are some general PostgreSQL related things that we would love to get help for, but not sure if that is EDB related enough so that it would be fine for you to contribute that back.
Either way, I would like to invite you to our chat platform Zulip in case you want to discuss further collaboration.