recipient_ids field appears to have been renamed thread_recipient_id. The script would not run for me until I made the update.

Thanks for catching this and bringing it to my attention! I would like to preserve backward compatibility with older Signal backups, so I think we should use some sort of test to handle both possibilities.

As a side note, this script can also export Signal's encrypted chats, but not images sent through encrypted messages.

Good to know. As I noted in the README:

My Signal databases contain only ordinary SMS and MMS messages, and not Signal's end-to-end encrypted messages, so I do not know whether sms-db will properly import such messages.

So now we know ;) Perhaps in the future I can work on that - in the meantime, patches welcome!

On second thought, I think your way is preferable: try to keep sms-db compatible with the current Signal database format, and instruct the user to update the Signal backup to the current format (by installing the current version of the Signal app and having it do the migration by restoring from the backup and then creating a new backing in the current format).

For what it's worth, Signal's migration code has the details of what changes to the database format were made in each version bump; it looks like this one was made in version 108 ("THREAD_AUTOINCREMENT").