When you export your calendar, it is in an .ics file, both events and tasks. The ics file is a text file which can be edited. RFC-5545 defines the format.

When you export your address book, there are two formats: CSV is comma separated variables, and can be input to a spreadsheet. LDIF is also a text file and is better for importing into another computer.

As far as syncing, I'm not sure what you have in mind, but Google is one way to share that data between devices.

Thank you very much for the answer. So just keeping the same files on multiple devices, without manually exporting the calendar/address book is not an option? (i think its: C:\Users\<Windows user name>\AppData\Roaming\Thunderbird\Profiles\<Profile name>\ )

My initial idea was to just sync the profile, in order to have a shared calendar, tasks and the address book between my devices WITHOUT having to use Google or another "man in the middle".

The question is not how to sync, but if it is theoretically possible to copy/paste my thunderbird profile - including calendar, tasks and the address book between linux/windows/android and access my information on each device..

The Lightning calendar, in particular, has a binary component and is compiled specifically for each target platform. Hence if your profile contains Lightning, it won't be transferable between Windows and Linux. (Enigmail is another add-on with this characteristic.)

In my book, Android == Google; it's fighting uphill against the flow not to use a Google-provided method to synch with an Android device. TBH, I haven't looked hard at my Android tablet to see if it supports calendar or contact data file export/import, but having been around the menus and having looked at various 3rd-party file manager add-ons and having poked about in the filesystem, my feeling is that direct file transfer is not a use case they anticipated or chose to support. So my calendars and contacts synch via googlemail accounts.

And there is no official build of Thunderbird for Android, so your query about Android compatibility is I think somewhat hypothetical. ;-)

huh. that's somewhat of a let down.. but understandable.. so a simple profile folder sync is not an option..

It seems like there are three options left for me, either keep using Google, find some third party add-on which exports the required information periodically/on change in a general format or find another application/provider which offers a solution for my concerns.

thank you very much for the information.