Magnetic levitation is the way to go. Not that difficult to setup nowadays; the new ultra strong magnets are not that expensive.
Then just a couple steel plates and you are in business. A little foam or something on the sides to keep the suspension aligned... Abso;ute 100% isolation.
that isn’t correct. First of all, your design means there is some physical contact between the plates, if not the top goes shooting off to the side.
The other thing is it is not a magic carpet suspended in air. There is a force from the lower magnets pushing up on the ones on the top plate. Shake the bottom and the top reacts. It is NOT 100% isolation. it may be damped, but it is absolutely not 100% isolated.
and lastly, there is the question of leveling it. If the load on top is not symmetrical it will tilt. Not good for a turntable.
