The flat Earth models (if you are so bold you call them models) that you see in this forum are all falsifiable, and have been falsified a long time ago. They all predict specific apparent positions for the Sun, Moon, planets and stars, for any given day and time. They all predict specific distances between known places on Earth. And that is just the short list. The long list is far too long to even make it.
The true test for a scientific theory is not just that there are clear ways to find that it is wrong (falsifiability) but that those ways have been tested to a good level of certainty and found not wrong (non-falsified).
In another attempt at replacing science with word games, the flat earthers sometimes talk about falsifiability but do not give a clear model where anything falsifiable really exists, and other times they give something a lot closer to falsifiable, measurable models but do not talk about falsifiability.