On Saturday August 14, 2021 Debian 11 "Bullseye" was released!
As with Debian releases going back many years, included in this release was a build specifically for IBM Z. Release notes for the IBM Z and LinuxONE version can be found here: Release Notes for Debian 11 (bullseye), IBM System z.
Additionally, the team working on this could use your help! Learn more about the team and resources available for collaboration at https://www.debian.org/ports/s390/, including resources available and a link to their collaboration mailing list.
The Open Mainframe Project also now has a Working Group specifically created to help mentor the next generation of contributors. If you're interested in being mentored on how you can contribute, you can start by going to the Debian Working Group wiki page.