TbSync has been updated so the Google address book now syncs in both directions. It supports other services, but I haven't tested them.

https://addons.thunderbird.net/en-us/thunderbird/addon/tbsync/

CardDAV is supported in 78 if a preference is switched to true.

Thanks for the suggestion. I'm not sure if that will do what I'm looking for. This looks like it is for syncing your cloud accounts with TB's address book.

What I would like is have my TB address books on both machines in sync with each other. Maybe it is just not possible??

Syncing with a cloud address book is currently the easiest way to sync contacts between machines. There is an add-on that performs a kind of syncing:

https://addons.thunderbird.net/en-us/thunderbird/addon/addressbooks-synchronizer/

Thanks I will take a look at that one. I understand about it being easier to sync via the cloud, just like with phones. Easier to transfer or sync from old to new via Google Drive or iCloud.

I would like to chime in on this subject as well. Migration of address books is relatively easy through exporting. It generates a CSV file that can then be imported.

But I find the Firefox Sync feature wonderfully effective. Would be nice to have basic configurations synced and have address books be optional. I just finished setting up a Windows 10 laptop and had to set up my e-mail accounts manually. A bit tedious.

TbSync has been updated so the Google address book now syncs in both directions. It supports other services, but I haven't tested them. https://addons.thunderbird.net/en-us/thunderbird/addon/tbsync/ CardDAV is supported in 78 if a preference is switched to true.

No longer works on latest version.

It works here in TB 78. You must also install Provider for CalDAV & CardDAV and toggle extensions.dav4tbsync.googlesupport to true in Config. editor.

There doesn't appear to be any working solution to syncing address books or msg. filters. Can cloud storage be used as LDAP server?