Yes, exactly. But at least you can have an e2e encrypted relay as syncthing does.

This problem is similar to the one faced by Matrix on iOS, and they provide the notification service. All of your conclusions apply though.

This could be worked around, in theory

When you begin hosting you have to wait a bit before your email doesn’t go to spam, at least that was my experience in 2018.

Edit: I just checked and I can now deliver to Hotmail/MS365 too!

This should be at the top

2. With microk8s you can, but you’ll need Windows Server Datacenter (iirc) and the ecosystem is a mess… there are not many images built for Windows and, worst of all, the image Windows version must match the host