The muzzle device thread pitch for the SCAR 17/S is 5/8x24, which matches that of the LaRue brake. The problem is timing it.
Some argue that the 17/S lacks a sufficient shoulder to support shims needed to time muzzle devices that require it, such as brakes. For suppressor mounting, the jam nut used on the OEM muzzle device is alleged to not allow for a square orientation of the muzzle device, which could increase the risk of baffle strikes. OEM suppressor mounts (i.e., FN ECP, AAC Blackout) reflex over the barrel to deal with is. I do not believe the LaRue does.
For my 17S, I use a SF SF3P-762 which doesn't have to be timed. I just index it off the muzzle.
Some people may have experience using a brake wthi a suppressor on the SCAR. I'm not much of a brake fan, so I'm not concerned about it. If LaRue comes out with a flash hider that needs no timing, then you shouldn't have problems.