Some flat-Earthers discovered images of multiple suns in the sky. They jumped to the conclusion that it proves whatever they want it to confirm. In reality, we can explain them without going for farfetched scenarios.
An object is visible if it is either reflecting light or a light source itself. Furthermore, a reflecting object can have specular reflection (glossy finish, mirror-like), diffuse reflection (matte), or the combination of both.
Some flat-Earthers like to compare the appearance of the Moon to a glossy, metallic ball. Then, the difference in how the two objects look is taken as “proof” that the Moon is not reflecting light. They are wrong. A shiny metallic ball reflects almost all incoming light in mirror-like fashion, or that it has predominantly specular reflection. On the other hand, the Moon reflects incoming light to every direction, or that it has only the diffuse reflection.