I have never seen contributors get anything for open source contributions.
In larger, more established projects, they explicitly make you sign an agreement that your contributions are theirs for free (in the form of a github bot that tells you this when you open a PR). Sometimes you get as much as being mentioned in a readme or changelog, but that’s pretty much it.
I’m sure there may be some examples of the opposite, I just… Wouldn’t hold my breath for it in general.
Plex runs relay servers where your Plex server will connect to the relay and your player will also connect to the relay, making both ends of the connection egress type as far as routing and access control goes. https://support.plex.tv/articles/216766168-accessing-a-server-through-relay/
It’s optional and likely not everyone uses it, but this provides a way for Plex to do remote streaming without the Plex server being reachable directly from the internet.
Separately, it costs money for Plex to run.