Linux Distributions Working Group
Mailing list: https://lists.openmainframeproject.org/g/wg-linux-distros
Slack channel: #linux-distros-wg
Distribution-specific resources
Debian
The Debian s390x team has a mailing list at: https://lists.debian.org/debian-s390/ and their own port page at https://www.debian.org/ports/s390/