Welcome to the forum.
Ideally i assume a dashcam should be chrome plated to reflect heat from the sun rather than absorb it like a black camera would do.
But this make the camera highly visible and so you risk : 1. getting the camera stolen when parked - 2. A part in a alteration see it, which would be unfortunate if that person are already aggravated and hoping to get by lying.
In my opinion the best solution is the systems where the cameras are remote from the main unit where the heat generating encoding and storing go on, that unit could also be made larger to accommodate actual cooling VS the meager heat sinks in conventional dashcams, also it can be placed out of direct sunlight, and you could actually use active cooling in parking guard mode, though this would cut into total time parking guard is possible.
Also theft of the main unit or just the memory card in it will be harder if it is hidden.
Edit for regular use just recording when driving, and just sitting there cooking but not recording in the sun, well the black cameras are fine.
Heat problems when driving are not really existing, even if you have a car like mine that dont have AC, and just sitting there shut off, though in a hot state in summer the camera will be almighty hot as will the car interior.
But a good camera will still wake up when you start the car and record your drive.
I have not heard of a camera needing AC to get going before it was cold enough but i have heard of dashcams so cold that they would need a few minutes for the car to warm up before they would work.
You can maybe run into heat problems ( when driving ) if you use am modified firmware with a substantial higher bitrate, cuz more bitrate = more heat, and the dashcams like action cameras do not have impressive cooling solutions.
But as far as regular bitrates go i have not heard of a dashcam overheating while driving, it is only using parking guard and parked in the sun where heat get to be a issue.