You can have the barrel braked without threading it. Most hunting rifle brakes go this route. Magnaport is an example. It's generally much cheaper if you don't have a separate need to have it threaded, and if you intend to use the brake all of the time.
A few reasons to thread it would be to add a suppressor or muzzle tuner in the future, or to add a brake built as a suppressor adapter, such as the Brakeout.
If you thread it, go 5/8-24, which is basically the standard for the above.
Look around locally for threading. Expect to pay $150 or more+ shipping if you send it out. That's before the actual brake cost gets added.
Try someone like Adco Firearms in OH if you send it out.
I'll add that I detest muzzle brakes. I had a braked BOSS on a 7mmRem Mag, and decided I would rather have the recoil than the massive increase in blast, which makes me flinch like crazy. I added a non-ported BOSS to it instead.