Version 1.0.0 of my HTTP/2 client library is available as a pack (installable with ?- pack_install(http2_client). Source is at https://gitlab.com/jamesnvc/prolog_http2_client.
It is functional enough for me to have had it running in production for the past few months, but be warned that it is not terribly robust in the face of misbehaving servers.
I would like to eventually move the functionality in to the built-in http_client library, but unfortunately the nature of the HTTP/2 makes this somewhat annoying (e.g. since HTTP/2 is a binary protocol, one can’t simply write or read directly to the stream as usual; additionally, it can have multiple requests over one connection, so it can’t simply return a single stream).
Feedback welcome!