There are not much to do in the way of this, a few guys have used little cameras like mobius, and then glued them to the dash as thats just about the only way to get something to stick to that, and then throw a cap over the camera when parked as it is after all in a very visible location.
Routing a wire along the headliner to the A piller and down that are pretty east and often even tool less, having a wire dangle down over the windscreen are silly and even illegal here in Denmark.
I have just take a dremel to my center console to be able to route a wire in a fashion i can live with, cuz i too cant have wired dangling no matter where it is.
And my relation to my little cheap mini car are in a place where taking a dremel to the center console plastic dont bother me, the little car have no resale value all when i sell it some day, will be much better as part of a trade in for a new car where i could get much more than the resale or scrap iron value.
Even if i should sell the car some day, the buyer will be looking for a cheap car that just passed its last inspection so he / she have a fairly cheap car to drive for 2 years before the next inspection.
But most dedicated dashcams are not meant for on dash install, so one would have to get creative here.