Because sometimes a photo may be used to prove something and you do not want the user to take several photos a single time with his camera and then upload those photos inside AppSheet other times.
If not possible, is there any way to be sure the uploaded photo was taken (not uploaded) in a specific date/time?
I just tried your solution. It seems like the setting affects the behavior in the Appsheet container app but not the browser version. As soon as I open my app on my smartphone in the browser, I can still choose a file instead of being forced to take a new photo even though I disabled “Allow image input from gallery”.
Maybe, if the user has android, make a copy of the app (so they don’t know the link), set same sharing options, make an APK of the app and sideload it to their phones. Remove their appsheet app.
If you don’t trust them at all then generate and store a random code in the app each day. Make them write the code down on a piece of paper, and take the photo with the code visible.