1. Watch a sunset. The Sun goes over the horizon (not around in circles overhead).
2. Clouds high in the atmosphere stay lit longer at sunset (and light up earlier at sunrise) than clouds lower in the atmosphere. It'd be the opposite with a "Spotlight sun", which would project a cone of light onto Earth, wider at the base than the top.
3. The Sun's apparent diameter never changes. It can't be a little ball flying around in circles overhead, because it'd get smaller when it's farther away.
4. Watch a lunar eclipse. The shadow of the Earth is curved.
5. If you are in the Northern hemisphere, find Polaris, i.e. the Norh Star. At night, all the stars go counterclockwise around it. Its angle off the horizon is exactly your latitude. Go to the Southern hemisphere. No Polaris, it's over the horizon ffs. But there is a south pole point you can find by using the southern pointers. All the stars go around the south pole...clockwise. [1]
6. Like Polaris, the constellations disappear over the horizon as you move south.
7. Go to the ocean. Watch a ship sail away. It disappears hull first over the horizon. Use binoculars. You can see more of the ship if you are higher above the water. The ocean is curved.
8. Watch the Sun for a year. It moves through the Zodiac (i.e. against the background stars). That's because the Earth orbits the Sun, duh.
9. Take a flight from South America to South Africa. Take a stopwatch if you don't believe clocks are real. Planes would have to be supersonic to fly the greatly exaggerated distance of a disk Earth.
10. Look through a frickin telescope. Literally every planet and star and moon we see is round. Why would the Earth be different?
11. Swing a pendulum for 24 hours. It won't just rotate back and forth. Foucault showed a free-swinging pendulum will rotate in a circle because of the rotation of the Earth. You can even compute your latitude from the speed at which it processes.