Why Denmark is dumping Microsoft Office and Windows for LibreOffice and Linux

They even said that if it proves too difficult, they will return to Microsoft

And, unfortunately, I'm pretty sure they'll decide it's too difficult. They'd need capable linux-admins and helpdesk personnel, training for employees and someone to deal with the people who just won't even try to change. All of that costs money (and time, but that's the same thing), and quite a lot of it at first and benefits will come slowly over time.