https://canadamats.ca/collections/horse-stall-mats/products/re-vulcanized-rubber-stall-mats-straight-edge
This is what I have under my car, currently up on stands. My house was built in '61. No moisture barrier under the concrete. The mat is 1" thick, pretty much indestructible, takes the weight of my car on the stands and allows my jack use, no problem. Takes a pounding, dropped tools aren't messed up, actually comfortable to be on if I'm working underneath. Spills are nothing burgers and essentially any moisture that would want to emanate from below the car can't. That leaves ambient humidity which neither my mat nor plywood laid on the concrete would address.