What flat-earthers believe in place of gravity

 1. The Earth is accelerating upward at a constant 9.8 m/s²

This claim was made by The Flat Earth Society (I haven't found a source for this).  Flerfs get very angry about this explanation and typically say things like "The Flat Earth Society is controlled opposition".  I suppose this means that they think that the FES is trying to deliberately make flat earth look ridiculous, as if it needs help.  

A typical criticism of this claim by debunkers is, if this were true, Earth would have long ago exceeded the speed of light, but this is mistaken - length contraction and time dilation would prevent an constantly accelerating body from reaching c. 

2. Electromagnetism

This usually involves a large amount of handwaving and word salad, and still fails to explain why electromagnetism both attracts and repels, but gravity only attracts, and why a Faraday cage can block EM but not gravity.  But flerfs don't deny gravity because they want flying cars, they deny it because gravity tends to make planetary-sized objects roughly spherical, explains why water isn't flung into space like a spinning wet tennis ball, and why the atmosphere doesn't need a dome to keep it contained.  So if EM is why we aren't floating, why wouldn't it also make big masses spherical and keep water and air on them?

3. "Density and Buoyancy"

Flerfs will repeatedly mock gravity, saying that if it was real, it would cause objects to "stick" to Earth, but and post photos of oranges in water, or metal floating in liquid mercury.

They ignore that buoyancy requires gravity.  Repeat these experiments in zero-gravity, and buoyancy vanishes.  And one doesn't need to go into orbit or even an airplane simulating weightlessness.  Just dropping something off a building will suffice.  It's probably safer to try that with the two oranges than an anvil and mercury