I don't find the link any more, but there was a video somewhere of a timelapse from the view out of a planes cockpit, and the flight was from Europe to Africa at night, like 4 hours or so.
And you could see the nightsky with the stars, but over the whole flight the stars were not moving upwards. They just rotated a bit. If Earth has a curve, and the plane is following that curve, the stars would have to look different after hours of flight. Stars that would be below the horizon in Europe would be visible in Africa. If the stars stay in the same distance to the horizon, there's only one explaination: Earths surface has no curve.
Sure the video could be fake, like every video, like "footage" from the ISS, like lasers over a lake, so I don't say that it's evidence for anything. It just is, in theory, a way to get evidence for or against the curvature. You sit in the cockpit of a plane and make a video of the nightsky. Then you would know.