> lack of sunlight, shouldn’t be a huge issue on mars.

Mars only gets 43% as much sunlight as Earth (https://en.wikipedia.org/wiki/Mars). On top of that, Mars's lack of a magnetic field like Earth's makes cosmic radiation there worse to the point that colonies will likely be underground, or behind heavy shielding aboveground: https://phys.org/news/2016-11-bad-mars.html

I stand corrected

Mars has significantly less sunlight (in terms of irradiance) than Earth

That might be more of a problem in the higher latitudes, but on Martian equator, sunlight at noon will be comparable to sunlight at noon somewhere around the Baltic Sea - still perfectly fine. Also, Martian atmosphere is thinner and blocks less light than ours. (Unfortunately it also does not prevent harmful UV rays from reaching the surface.)

One possible problem not discussed would be the giant dust storms that can cover large tracts of the planet for weeks. We don't have this kind of weather on our cradle planet.

True, but a day on Mars is pretty much the same length as on Earth, which is great for the human cycle. Googling says that lux 100k on Earth would be roughly 44k on Mars, so a lot dimmer, but still better than months of darkness on end.

Now the real question is whether colonists can/will live on the surface? But then a secondary addition, due to modern technology we now have much better lighting that can approximate natural lighting, even underground.

In every book I've read on the subject they mentioned going underground to protect against radiation. The lack of a thick magnetosphere apparently means any surface equipment / personel would be subject to unacceptably high quantities of solar radiation. I guess living in a hole on another planet isn't as glorious as giant geodesic glass domes but I sure hope somebody does sign up for it.

Colonists would still have to deal with months of almost darkness during dust storms.