The question of dash cam fitting comes up a lot on this forum and elsewhere and I think the answer to hard wiring comes down to the fire risk and possibility of invalidating the manufacturers guarantee so it’s OK for the dealer to hard wire it but not us.
You know how it works, your gearbox falls out of the bottom of the car and the manufacture says you hard wire a dash cam so cannot accept any responsibility for the gearbox falling out of the car.
Extreme I know but any excuse will do.
With my current car I’ve gone the way that Wayne suggested, not that I can do it myself because of my disability but my grandson is a dab hand at removing and refitting interior trim while the wire makes its way to the centre console where my 12v accessory socket is he was able to tuck the wire behind the roof lining, easy to do on most cars, then route over the passenger side foot well. Then he removed the cowl of the centre console, pulled the wire through and into the 12v socket.
Removing and refitting the centre console needs a bit of thought as you don’t want to cause any damage to it but lucky for me the part on my console only required a tiny bit in front of the gear shift where there’s a slide away hatch that hides the 2×12v sockets plus inputs to the infotainment centre so closing the hatch and everything is out of sight.
All back together and not a wire in sight except that is the rear facing camera but that’s sort of out of sight anyway, I’ve not got eye’s in the back of my head ,? and this connection was as simple as sticking the camera on the rear glass and plugging it into the 12v socket there in the boot.