@lduboeuf
I think that I can as well note here the results of my sunday tests with Radicale and UT, it will allow me to retrieve them easily and maybe be of some usefulness to others: it works with 24.04-1.1 stable, but it can be quirky.
I used a test server that has already other databases, notably an address book, and these database were proposed as options for sync with the calendar.
It's already a problem since an address book is not a calendar.
However it got worse since even after selecting the right database, the sync failed repeatedly until I deleted the 'wrong' databases. The server reported a 400 error on some query aimed to the address book (why oh why since I asked specifically to sync with the calendar...) and the whole sync was failed (I guess that Google Calendar has not this problem since it's just a calendar, it does not try to support all kind of Dav databases like Radicale do)
This was reported by a red indicator in the UI, however the detailed journal was not particularly enlightening, it reported error codes (10400 ? I guess it was error code 400 with database number 10 - so very Unixy error reporting )
The whole testing was not made easier by the syncevolution user interface, a software that has a conception of 'user friendly' that is decidedly selecting its friends. I had to delete the offending files with 'rm' in the evolution (not syncevolution) directory via the command line to get rid of the excess databases in the UI, while they all got back when I deleted the last one (the calendar).
Finally butchering my test server was the right option (and now I don't have any failing test case anymore ).
