nghttp2 v0.4.1 just released today. It is mainly a bug fix release. The supported HTTP/2 protocol version remains h2-12.

Although this release is tagged as bug fix release, nghttpx got some improvements. Firstly, --npn-list option now works with ALPN. Secondly, * is officially allowed as <HOST> parameter in --frontend option and it means wildcard address, which can bind to both IPv4 and IPv6 addresses.