Our IT allso fight with GPO changes happenign from 2019 to MS365. One of our IT. Told me they may test Thunderbird, as it get an Exchange integration.

Thanks for the hint. Long ago I also used syncthing. At that time it not fit my needs. But in this case it may is a possibility.

Any best practises for excluding files in Home for syncing like .cache ?

As far syncthing does not come with a vfs.

All family member I support and provide with services use a Laptop. They are connected over wireguard. Solutions that depends on Network connections will not work.

Someting like that on a Keyboard as Key woukd be nice. So I could dynamically switch the Key description of the current keyboard settings.