[neild]

HTTP/3 is almost indistinguishable from any other protocol running over QUIC, and QUIC itself is almost indistinguishable from random noise in UDP packets. If you want to masquerade as HTTP/3 traffic, just using UDP on port 443 will generally be sufficient.

(Only “almost” indistinguishable, because it’s possible to decrypt the first packets of the client’s handshake and examine the ALPN parameters used to negotiate an application protocol. And QUIC may be further distinguishable from other UDP traffic through statistical analysis of packet sizes and response latencies, as well as the few unencrypted header bits.)