> Backblaze B2 invented their own API, so no tooling at all.

At first that was true, but now we have a list of 3rd party tools you can use. Check the list out here: https://www.backblaze.com/b2/integrations.html

Here is a sample from that web page: CloudBerry, Rclone (mount B2 as a hard drive on your desktop), Synology (this is a NAS drive), Retrospect, Cantemo, Cubix, Cyberduck, Duplicacy, Duplicity Linux, HashBackup, NyNAS, NeoFinder, Odrive, Qbackup, SmartFTP

They do, and there is a CLI tool provided by OpenStack themselves: https://docs.openstack.org/cli-reference/swift.html

I think by "decent tool" they meant "decent wrapper program" rather than "tooling for programming with the API".

Guess I must be blind then. Are there any sync programs which work with it?