Yes - the SmartThings integration does still require the Harmony hub.
The hub is, of course, included with many of the new Logitech Harmony offerings (including the latest Harmony Elite). But, if you purchase a remote without a hub, you won’t be able to hook it up to SmartThings (or at least, not until you purchase a hub and connect your remote to it (assuming the remote you purchased can connect to a hub…)).
Phew - convoluted, but you can buy hubs and remotes separately, and not all remotes connect with the hub…
Safest option if you don’t understand the product family - buy one of the newer remotes bundled with a hub, e.g. the Harmony Elite, or one of the remotes listed in this post (which predates the Elite) (if you follow the link to the post you’ll find the content is formatted much better than the preview here):