FOSS to the rescue:
* LibreOffice, instead of MS Office.
* Thunderbird, instead of Outlook (even though I don't like the direction Thunderbird has been going).
* NextCloud, instead of one drive (and there are other alternatives, more FOSS-friendly or less so)
* Matrix/IRC client plus Jitsi, instead of Teams.
and they will do just fine - on Windows or on Linux.
Same one they were using before I would think. Nobody said they were using MS Exchange server.
> and compliance... oh my compliance
Is that a magic word? :-) ... Compliance with what?
FOSS to the rescue:
* LibreOffice, instead of MS Office.
* Thunderbird, instead of Outlook (even though I don't like the direction Thunderbird has been going).
* NextCloud, instead of one drive (and there are other alternatives, more FOSS-friendly or less so)
* Matrix/IRC client plus Jitsi, instead of Teams.
and they will do just fine - on Windows or on Linux.