>Nginx doesn't support http 3

nginx do support it.

https://nginx.org/en/docs/quic.html

And I see I was not that wrong; the module is still marked as "experimental" and not built by default.

https://nginx.org/en/docs/http/ngx_http_v3_module.html

ah okay i was wrong there, mea culpa

The guy's point still stands - lots of popular software do not yet support http3.