Flat Earth Society's Universal Acceleration: The Gravity Replacement Problem

Some Flat Earth Society material replaces gravity with “universal acceleration”: Earth accelerates upward at about 9.8 m/s², creating the feeling of weight. Many modern flat-earthers reject this, but it remains useful because it shows what happens when a flat model tries to replace gravity. 
 The Claim 
 Instead of objects falling because Earth attracts them gravitationally, the flat Earth accelerates upward into objects. Locally, this can mimic the feeling of weight. 
 Problem 1: Speed Builds Without Limit 
 Continuous acceleration of 9.8 m/s² quickly reaches relativistic speeds. A defender can invoke relativity, but then the model becomes much more complex than the simple slogan. 
 Problem 2: Gravity Varies by Location 
 Measured gravitational acceleration is not identical everywhere. It varies with latitude, altitude, and local geology. Universal acceleration alone does not naturally explain these variations. 
 Problem 3: It Does Not Explain Orbits 
 Gravity explains falling objects, tides, orbital motion, planetary paths, and satellite trajectories within one framework. Universal acceleration mainly tries to explain downward weight sensation. 
 Problem 4: No Mechanism 
 What accelerates the entire Earth upward? Through what medium? Why at that rate? Why does it also coordinate with celestial observations? 
 Direct Debunk 
 Universal acceleration is a patch for one local experience: objects fall. It does not replace the broader predictive role of gravity across tides, orbits, geodesy, pendulums, and measured variation in apparent weight.