"The north-German state of Schleswig-Holstein plans to switch to open source software, including LibreOffice, in its administration and schools.
In doing so, the state wants to reduce its dependence on proprietary software, and eventually end it altogether. By the end of 2026, Microsoft Office is to be replaced by LibreOffice on all 25,000 computers used by civil servants and employees (including teachers), and the Windows operating system is to be replaced by GNU/Linux."
This article by Mike Saunders shows several photos from the Open Source conference, also linking to an interview with the Digital Minister Jan Philipp Albrecht and a PDF of the Parliment’s Planning. (both in German)
What OS are they going for?
Unclear, but if I were to speculate, something in the Debian branch seems likely.