I just started playing with Linux on my old potato desktop. Although it is easy to get Thunderbird working with mails, I did not manage to sync my agenda (using outlook). Because Microsoft is depreciating Windows mail+agenda, I have to look for somethinng else on my Windows laptop also (using Microsoft Outlook on Android at the moment).
I could switch to using Google calendar (as primary on Android moblle, currently using Outlook for android), so using Betterbird on my Windows11 laptop and Betterbird on my Linux patato PC desktop, I would strike to flies in in one go (you are Dutch also
so you recognose the saying). So betterbird (on Windows laptop and Linux desktop) suddenly is a appealing alternative for me
Could please you post how you managed to sync Google Calendar (Agenda) with Betterbird or post the links you found