The appearance of sunset depends on atmospheric conditions. Thermal inversion can irregularly refract light coming from the sun and distort the image of the Sun seen from an observer.
Some flat-Earthers observed a specific appearance of sunset and presented the fact as if it “proves” a receding sun in the flat-Earth model. They are wrong. The appearances of the sunsets are the results of atmospheric refraction.
An inversion is a deviation from the normal change of an atmospheric property with altitude. Normally, air temperature decreases with an increase in altitude. During an inversion, warmer air is held above cooler air; the normal temperature profile with altitude is inverted. The phenomenon will affect how the atmosphere refracts sunlight and can distort the appearance of a sunset.