ATF will probably work too. Just don't put engine oil or brake fluid in your jack.
ATF works just fine.
I'd not use the newer products. At least when first introduced, Dexron VI and plain old o-rings didn't play nice. I don't know if things have changed, but I wouldn't use the new versions, whether GM, Ford, or FCA.
That said, Dexron III, especially the Mobil 1 version, was an excellent hydraulic fluid for cold winter to hot summer use, as in hydraulic garage door actuators.