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'We're done with Teams': German state hits uninstall on Microsoft
(us.afpnews.com)
This is a most excellent place for technology news and articles.
It doesn't say, but seems to be an ad-hoc solution.
This process started in 2021 already.
They will use GNU/Linux, LibreOffice, Nextcloud, Open Xchange (OX), Thunderbird and Univention AD-Connector.
https://www.computerwoche.de/article/2833398/schleswig-holstein-verabschiedet-sich-von-microsoft.html
https://www.schleswig-holstein.de/DE/landesregierung/themen/digitalisierung/linux-plus1/Projekt