It seems there was a miscommunication and a contractor painted the concrete floor by mistake. I know that the proper way would be to remove the paint but I try to avoid that because overall project progress is too far (walls painted, cabinets built in, some ornamentals in place, ...). Now I try to mitigate, not get to the ideal solution.
The concrete slab was painted with 1-part epoxy acrylic paint. I called the manufacturer and they say that the only thing that might help is to apply a primer/sealer on top of it. They have an acrylic product that can be applied after roughing up the surface (manually roughing up the surface is as far as I can go in terms of making a mess).
It is an indoor low traffic area so there wouldn't be a lot of stress on that floor and the plan is to put a layer of floating hardwood on top of it. Even though the variation in height seems no more than 1/2 inch, there are small and big craters and bumps all over and the floor is very uneven. It doesn't have to be leveling compound, it could also be some sort of construction adhesive, epoxy or whatever.
I would appreciate any pointers to whatever could be applied here to level the floor.