Not sure if this could work for you, but I use HAProxy (not for failover, but just as a front end). It terminates TLS and supports http3. I was already using it

Not sure if this could work for you, but I use HAProxy (not for failover, but just as a front end). It terminates TLS and supports http3. I was already using it for http2 (TLS required for that), so enabling http3 involved upgrading and editing the config a little bit. I'm pretty sure the web servers behind it use http1.1 to HAProxy, then HAProxy talks http3 to clients. https://www.haproxy.com/blog/announcing-haproxy-2-6 https://www.haproxy.com/blog/announcing-haproxy-2-6 https://haproxy.debian.net/ https://haproxy.debian.net/ Live example: https://theandrewbailey.com/ https://theandrewbailey.com/