It's not just office, SH and many other parts of the German government have been slowly replacing the entire O365 suite with OpenDesk, which is an open source product based on Matrix, Jitsi, LibreOffice, and a few other tools.
The goal is to have a fully integrated solution for calender, chat, calls, documents, cloud storage, etc.
My employer is developing parts of that solution and we recently switched our internal communication over to it, and tbh, it's working really well.
Now is the perfect point in time to do it, with the GDPR ruling regarding O365 and Microsoft fumbling the migration between old teams and new teams.
That may be true, but at least the genes for night owls are present in more people than the genes for early birds.
So it should be expected that, regardless of phone usage, over half of the population will go to bed and wake up ~2-3h later than expected.
If your timezone is closely aligned with the sun, that'd be 22:00-06:00 for early birds and 01:00-09:00 for night owls. But if your timezone isn't, both of these times would shift around.
For me personally, no matter when I go to bed, whether it's 22:00 or 03:00, I always wake up precisely 09:30 without any alarm clock. But this also means if I have to wake up earlier, e.g. at 8am, I'll be very tired and not well rested.