This prompted me to start researching dbkiller inserts. Cheaper and easier to fit than I thought they'd be (about $5-$10, available from ebay, amazon, aliexpress, etc).
There appear to be two "universal" styles.
One goes up the wazoo and comes in a variety of sizes to accommodate different exhausts. It's held in by a bolt -- if you have some pipe sticking out of the rear of your muffler you can drill a corresponding hole for the bolt, or (presumably) run the bolt in from the inside and use it as a set screw. There's a movable baffle at the other end of the thing so you can adjust sound level (with the obvious tradeoff of greater restriction).
The other style drops into your muffler from the engine end, no bolts. Less to go wrong, but for 2" pipes only and not adjustable. You take your muffler off, put it in, and reinstall the muffler. That may or may not be easy. I tried taking the can of my R6 (which has been on there for over a decade) and no way.
In between this and Tamworth's noise craziness, seems a smart move to chuck one in the spares box, just in case.