It took far too long, given the huge benefits of HTTP/3 for mobile web users, any performance-focused website already moved to CDNs (like CloudFlare) that supported it long ago (even when it was still named QUIC and Chrome-only).
Amazon CloudFront now supports HTTP/3 over QUIC for end user connections. You can enable HTTP/3 in all new and existing CloudFront distributions on all edge locations worldwide at no additional charge.
I don't like the unencrypted tracking ID that comes with QUIC (thanks Google)