Recently installed a dash cam into the car myself. Did it on my old Evoque as it was pretty simple so had a stab at it again in the RS4. Bit more tricky on this car, as the A piller removal and reinstall was a bit tricky. But paid to access Audi Erwin ( few quid an hour) to access workshop manuals that show you how to remove Trim so you can route the cables down to the fuse box in the passenger footwell. I downloaded the manuals for the A Pillar removal and Fuse assignments (to make sure wasn't tapping any critical components), which are all in the passenger footwell for Live and switched. Confirmed with a multi-meter. The passenger end panel fuse box has a good earth point. PM me if you want any further details.