Which natural stone slabs are less prone to moss/discoloration?

Color: Bianco fine, homogeneous surface thermo-sealed facing with natural stone grains in color and UV-resistant color pigments INTRACLEAN for a dirt-repellent surface

With this "high-tech description" they shouldn’t get dirty at all.

You should be able to clean the slabs with water and a "scrubber," since the dirt is only superficial.

How "bad" do they look? Pictures?
Cleaning only in spring, right?

often it is already sufficient to spray off with the garden hose..

You should be able to clean the slabs with water and a "scrubber," since the dirt is only superficial

that depends on the type of moss:

especially older concrete slabs develop very thin porosity channels after years.
Some moss roots can grow into these.

If you scrub the surface, the roots remain in the thin
channels and keep growing out of them.

You can only get rid of that finally by thermal overheating (sterilization).

How is it best to clean these if a high-pressure cleaner is not to be used?

We switched last year in the courtyard (concrete paving stones) from high-pressure cleaning to brushing off with a broom using only water after pre-treatment with baker's yeast, the water comes from a hose with a spray nozzle. So less pressure. In my perception, high-pressure cleaners have an ambivalent effect: the high pressure only splashes away a little more than what it had previously forced deeper into the pores. The soda lye reaction removes the dirt better than the brute force attack with the high-pressure lance.

We have travertine slabs and they can be cleaned well in spring with a brush/broom and some water.

Hoihoi, thanks for your opinion. Then I will take the brush in hand in spring. Better safe than sorry