There is TbSync 4.1 for TB 128, but there appears to also be a way with the built-in CalDAV:

https://www.reddit.com/r/Thunderbird/comments/1f1kxxq/comment/ljzvtgs/

Thank you very much for your answer.

It is a pity that Mozilla can not post a short note about that topic...

Brgds,

There is TbSync 4.1 for TB 128, but there appears to also be a way with the built-in CalDAV: https://www.reddit.com/r/Thunderbird/comments/1f1kxxq/comment/ljzvtgs/

That version is for 128.0.1. I have version 128.1.1esr. Apparently there is no way to sync with ICloud?

TbSync for providers like iCloud has been discontinued since CalDAV and CardDAV are built in. Use the method suggested in the reddit topic.

sfhowes said

There is TbSync 4.1 for TB 128, but there appears to also be a way with the built-in CalDAV: https://www.reddit.com/r/Thunderbird/comments/1f1kxxq/comment/ljzvtgs/

That version is for 128.0.1. I have version 128.1.1esr. Apparently there is no way to sync with ICloud?

I have 128.1.1esr and I was able to synchronize my iCloud contacts; did not try my calendar but I assume it would be largely the same process.

For contacts, I removed the old iCloud address book from TBSync that stopped working when the CalDav addon was sunset, then clicked "add CardDav Address Book" in the Thunderbird UI above the list of address books, then provided my Apple account user name and the CardDav URL that I saved from my old TBSync settings and clicked ok. Then it prompted me for the app-specific password I created for Thunderbird in my Apple account settings; once I pasted that in and clicked ok, my address book appeared (though it still isn't smart enough to download the contact photos, which is annoying. See related bug ).

Based on the Reddit thread mentioned above, the iCloud calendar sync is even simpler.

Second time around the Reddit thread worked. My problem was I wasn't using the app-specific password.

Thanks everyone