It's been ages this package has been marked unstable; where as I use it everyday and it works fine.
commit 48ab81a186cc23aca3b4efa1b90ab1260b94b25a (HEAD -> master, origin/master, origin/HEAD) Author: Hans de Graaff <graaff@gentoo.org> Date: Mon Sep 21 19:40:25 2020 +0200 dev-ruby/curb: amd64 stable, bug 743730