I recently installed a Kawa D11 dashcam with a hardwire kit and connected it via the Options Connector (I bought the male pin on AliExpress for 4). It includes both front and rear cameras. On the A-pillar, two cables go under the airbag, and then another cable runs under the floor to the rear window, where the last 15 cm of cable is exposed naturally to connect to the rear camera.
P.S. The main problem was that this was a new car, and I accidentally damaged the ceiling a bit while mounting the cables. Its much better to do the whole operation with plastic tools rather than with your hands.