Nextcloud has a similar file storage like SharePoint/OneDrive minus the content types and taxonomy trees, but I doubt you need those. If you use Only Office as online Office App in Nextcloud, you have a comparable UI to Microsoft and it uses Office Open XML (docx, pptx, xlsx) as standard file system.
I don’t know what a paid hosting for your team would cost, but it could be worth it.
MangoCats@feddit.it 8 months ago
That always helps. It also helps politically that M$ is based in a country that’s outraging the Danish people on a fairly regular basis…
Back in 1990-something, I got our office using Ami Pro - it was a vastly superior word processor to anything else available at the time. Then, a couple of years later, we started sharing documents back and forth with business partners via dial-up internet and that was the end of Ami Pro, all our partners used M$ and file format translation / import / export was nigh impossible in those days.