ekr____ 9 hours ago

Basically none.

First the success rate of any new IP-based protocol through most devices is incredibly low, especially now that NAT is so common.

Second, part of why QUIC runs over UDP is because the operating system generally won't let applications send raw IP datagrams.

Even running over UDP, QUIC has nontrivial failure rates and the browsers have to fall back to TLS over TCP.

frollogaston 13 hours ago

It's probably too hard to get NATs to agree on a new L4 protocol.