Google should've just called this HTTPS+ Everywhere and there'd be no blowback.
But also the spec itself is bad: "MUST" in capital letters when talking about setting up the HTTP3 endpoint and verifying the cert. https://datatracker.ietf.org/doc/rfc9114/
There are compile-time flags you can use to enable it in the QUIC HTTP/3 libs you can then manually link when compiling your personal browser. But with Google/Microsoft/Apple/Mozilla browser binaries used by the public they will not be able to connect.