Here are two direct passages from the Flat Earth Society's website:
What Is Gravity?
Gravity as a theory is false. Objects simply fall.
In the flat earth community there are several theories as to why this happens. Some attempt to explain this with use of mechanics like electromagnetism, density, or pressure. Others make use of traditional mathematics, such as the infinite plane model, and others a new look at the problem - such as the non-euclidean model.
What is certain is sphere earth gravity is not tenable in any way shape or form.
Is the Earth is accelerating upwards?
No. This is popular theory among some small groups to explain gravity, but it is problematic at best. The Earth Is Stationary. We are not whizzing about in space at 67,000 miles/hour or at speeds accelerating towards the speed of light.
Source:https://theflatearthsociety.org/home/index.php/faq