>It's not P2P, it's federated.

It's both. PeerTube instances federate with each other, but the video player uses P2P to spread the load between viewers.

Some of the instances choose not to federate with others. For example https://tilvids.com/ Here they explain why: https://mstdn.social/@tilvids/106902477087882284

I'm not sure webtorrent have a way to do peer exchange without centralised trackers like e.g Bittorrents PEX does, so if the core websocket trackers go down, are peers still able to share lists of known peers with each other or is the peer discovery centralised to the webtorrent/websocket trackers?

https://tilvids.com/ has some buffering but was much better compared to other links in this page. I guess the other sites dont have lot of peers in Australia.

Even if a specific video doesn't have a lot of peers, people can setup a server close to you to replicate popular instances you'd like to ease access to.

So you could have a peertube.au instance dedicated to seeding content from other instances on an opt-in basis (instance following other instances, and giving them a certain disk quota).