I Can Science That organized an effort to observe the sun angles at multiple latitudes at solar noon on 2021-06-20. This is an interactive visualization of the resulting data.
Please see Solstice Observations – An Interactive Display by I Can Science That for further explanation.
Drag the diagram to change the hypothesis between a hollow Earth, a flat Earth and a globe Earth.
For each angle measurement, an error is estimated by calculating the difference to a linear least squares fit of all the measurements. The measurements with a high error are shown with a less visible color.