I think I’m looking at original floorboards, rotting underlayment on top of those, a delightful assortment of other boards on top of that, then Pergo flooring.
I’m unsure of the best way to proceed. My gut says to pull up the top layer of boards to remove that underlayment, but then I worry that that turns into ripping up the whole floor.
(Left Side cabinet)
(Right side wall)
My house looks like this. I laid flooring not new cabinets. The builders laid flooring under the cabinets. I used some off cuts to fill the gap to let the dishwasher be level.