This question is prompted by this issue: mossdef-org/luci-app-https-dns-proxy#9.

In short, I'd like to be able to query the libcurl4 support for http2/http3, my options as I see them are:

1. If curl is not found, return that the support is unknown to the luci app and treat that return result accordingly.
2. Make curl a dependency of the luci app (which comes with the list of the public DoH resolvers, hence the need to determine http2/http3 support to know which ones to display as an option).
3. Create a helper binary -- that would be the most time-consuming for me.
4. Have the https-dns-proxy display the http2/http3 support in libcurl4, just like curl can do.

I wonder @aarond10 if it would be easy for you to implement the option 4 so instead of using curl as a front-end to libcurl4 I could parse the output from https-dns-proxy binary itself to discover wherever http2/http3 are supported.

Thanks!