Seemed fair as it powers main site !
Didn't add it because it's not merged into upstream and not in a standalone repository, but there's a Pelican plugin too https://github.com/asciidoc3/pelican-plugins/tree/asciidoc3_reader/asciidoc3_reader. PR is here https://github.com/getpelican/pelican-plugins/pull/1081.
With a little more efforts, looks also possible to use Hugo https://blog.anoff.io/2019-02-17-hugo-render-asciidoc/.