I ride the 24" quax muni with Magura brakes fitted. You will need to buy the older black CroMo frame with the brake bosses welded on from UDC.
I’ve included a couple of pics of my setup. You will notice the welded brake bosses from the side view (sorry - it’s a bit blurry cos i used my camera phone).
Also note the crazy angle of the brakes. This was to provide clearance with the Leopard 24x3.2" tyre, otherwise they would rub the tyre sidewall. These are angled down as far as they will go. IMO the brake bosses should have been welded 3mmm lower.
I later changed to a DMR Moto RT street tyre. I could re-adjust the angle of the brakes for the slimmer tyre, but they are fiddly to set up so i’m going to leave them the way they are.