How to isolate a refrigerator?

FWIW... A gas refrigerator has no compressor and makes no noise. They work fine and are usually sold to folks who are "off the grid".

I checked out the Liebherr 'fridges when we were looking for a new one. They are very nice German products, but a bit unconventional in that they are very tall and don't fit in the average American space allocation for refrigerators. They have no fan motors, so they are quiet. Performance comes at a price though, starting a $5,000 for the least expensive unit at the retailer I consulted.

We had a gas fridge on our boat a long time ago. It ran on bottled alcohol and needed a flame. I house unit could probably be plugged in for the heat source.
Our boat unit? give it 24 hours untouched and it'd freeze stuff solid. I didn't appear to have a 'speed' control

No fan is nice, but no compressor would be better.

newer fridges are much quieter than old.

Upon further investigation, it appears, that vibration noise is coming from the AC unit located outside of the house, next to the wall, where my system is. Initially I thought, that it couldn't be the culprit, since the AC unit sits on the concrete platform, that is simingly is not connected to the basement wall, but maybe I just cannot see the whole platform, since it covered with soil, and it is somehow is transmitting to the house.
I will try pads under the AC and see what happens.
The fridge is a little tricky- it is squeezed in b/w the kitchen cabinets, so it's unclear, how I should put pads under it? I will have to wheel it out of that space, then put pads inder it, and then what? How do I move it back into the space? Engineers here- need ideas. I'm clueless.
I only have one idea sofar, actually two- one, is to put sliders under the pads, two is to put pads on the floor, then put a sheet of peg board, ot plywood on the top, and then wheel the fridge on the top of the plywood/peg board.

Maril555 that A/C unit is most likely sitting on a concrete covered foam platform that HVAC companies use when doing installs. They dig down about 2-3" and through some sand down to work this foam platform down into it and level it. There really should be no transmission of vibration from mthe unit to the house except through the refridgerant lines. It really is de-coupled from the house.
As far as the refidgerator. I would try to have a freind tip the "empty" appliance forward and use one of those "grabbers" you see in some hardware stores for people to reach items on upper shelves, and place the pads under each rear corner. Then lift the front and slide the pads under each front corner. Just a suggestion.