In unicorn master (git), it seems kgio was removed (or unicorn no longer depends on it), so Ruby 4 may work there. But there is no RubyGems release that includes this change.
I can run unicorn from git, but it needs extra “release-time” build steps (generate lib/unicorn/version.rb, build/install ext/unicorn_http with ragel, and copy unicorn_http.so).
Workaround PR (exact steps): https://github.com/catatsuy/private-isu/pull/853 My mail to unicorn-public (may be inactive): https://yhbt.net/unicorn-public/20251227071714.D9328160070@mail.catatsuy.org/T/#u
Question: What is the best way to contact the unicorn maintainer, or request a RubyGems release?