Unless you get comfortable using linux, that's not happening. Microsoft groups so much into the O365 E5 tier that it's legitimately impossible to get a similar business level feature set for even double the price, mainly because win11 & office (word, excel, etc) make up 85% of that license cost on their own. So in order to have the business momentum required to make a software pivot you're going to need cost saving elsewhere to force it to make sense, and Microsoft has cornered the "I'm not a techy, just make it work like my computer at my last job" crowd that will never switch an OS because of their familiarity with Windows.

They go back to Skype for Business.

The linked article only mentions LibreOffice, Open-Xchange and Linux.

The following article mentions Libre Office Writer, Thunderbird, NextCloud as well as a later switch to Linux. That article explicitly says NextCloud will be used for chats, video conferences and file sharing.

handelblatt.de (German)

This official site mentions LibreOffice, Open-Xchange, NextCloud, cross-platform APIs, VoIP and a switch to Linux. It says that they generally want to use NextCloud for collaboration.

schleswig-holstein.de (German)

EDIT: TLDR: they switch to NextCloud Talk

The article also says they are switching to Linux, LibreOffice and Open-Xchange.

Now log in with your Microsoft account. No, the link was to your work email, you can’t log in with your personal email. Now you’ve logged in with your personal account, you’ll need to change to teams for workplaces. No, the new one. I’m sorry, that link was for a different version of teams, your account is showing unusual activity. We’re going to send a link to start the process of resetting your password.