That is untrue, you still need a server to facilitate discovery/passthrough. Peer-to-peer does not exist in the wider internet for most consumers.

> you still need a server to facilitate discovery/passthrough

You could just bruteforce IPv4 until you hit a peer that will give you a set of known peers.

I don't think pex/dht operate on 'well known' ports. in fact, I think most clients are configured to randomize the port they use on each startup.

most every client comes with a list of 'bootstrap peers' for dht though.

Trackerless torrents are very old now, they use the DHT network to find peers. I believe it needs to be seeded when you first start a newly installed client, but that's completely transparent to the user.