I’ve used the UCM and d’Brake (both external)
They both work almost exactly the same. I started a thread on it quite a while back. Post # 14 might be of interest to you.
I now use UCM with Schlumpf, and d’Brake on the other unicycles. They both work great.
EDIT: I forgot about the adaptor thing. The UCM uses front spacing so if you want to use a 180 disk you need the 180 front or 160 rear adaptor, for a 160mm disk you would need the 160 front adaptor. I believe it’s the same with the d’Brake but I would have to double check.