If you would like to play with HTTP/3 today, Cloudflare is providing a nice way to do so: HTTP/3: the past, the present, and the future
I do not use Chrome or Cloudflare service, but they also provide an Open Source implementation for both server and client in Rust: Quiche: Savoury implementation of the QUIC transport protocol and HTTP/3.
Firefox is also going to provide soon a nightly build that support HTTP/3.
HTTP/3 is becoming a reality faster than I expected.