h2 is HTTP/2 over TLS (protocol negotiation via ALPN). h2c is HTTP/2 over TCP.
https://blog.cloudflare.com/tools-for-debugging-testing-and-using-http-2/
Do HTTP2 if possible or downgrade
curl -I --http2 https://localhost:1234
HTTP2 or fail
curl -k --http2-prior-knowledge https://34.110.251.47 -v