Fedora 23 Server for z Systems (i.e. the s390x architecture) is now released and available for download. This release provides the new features and updates in Fedora 23 Server, but built specifically for the s390x architecture.
Refer to the Release Announcement and the Release Notes for general information on what is new in Fedora 23 Server, and the Fedora s390x team has a wikipage detailing notes specific to the s390x architecture on Fedora.