As noted in these questions, there are cases where foto uploads on iOS have their geolocation and other EXIF metadata removed (in safari):
https://apple.stackexchange.com/questions/326789/gps-exif-from-iphone-photo-upload-in-safari
Image upload from iphone strips exif data
As of now, I have not found a proper description of the circumstances when this happens. I have 2 devices for testing with the latest iOS installed where EXIF metadata is NOT stripped.
Is there a way to determine, most hopefully in the browser or from the upload, if the metadata has been stripped in order to show some kind of info to the user?
I can tell you right now that with my iPhone X and IOS 13.3 (current) the exif data is stripped if I use the default Settings->Camera->Formats setting, which is 'High Efficiency'. But if I change that to 'Most Compatible', the EXIF data is not stripped. These results are consistent if I do not manipulate the photo at all on my phone before uploading.
It looks like photos that are shot under 'High Efficiency' mode do upload with EXIF data if they have been edited on the phone first - but I have not done extensive testing to verify if this is always the case or under what conditions this always works.