The Tradfri line bulbs, plug-in pocket socket, and driver all work well with SmartThings.
The handheld buttons, remotes, “dimmers“ and other control devices have only partial integration and most people have not bothered getting them.
(It’s a similar problem to the hue dimmer for those familiar with those issues.)
The problem is that the handheld devices keep stealing the Mains power devices away from the SmartThings network. Or they will stay on the same network, but the handheld devices don’t send their button presses to the hub.
There are some people who have been working on it, but different people report different levels of success.