Thunderbird Pro will offer Thundermail email service, appointment scheduling, file sharing, and maybe even AI features. Email will be hosted on German servers.
FWIW:
The servers hosting Thundermail will initially be located in Germany with more countries to follow in the future.
I wouldn’t check that high level before asking which hoster they use.
I trust Europ but not AWS, GCP, and Azure less.
I suspect Hetzner since they specifically mentioned Germany and not a region like “eu-west” like other hosting providers such as Azure.