Manually Tag People/Faces in Photos for iOS Photos for macOS has the ability to manually tag People in a photo where the machine learning algorithm has not yet detected a Face:

Window &gt; Info &gt; Add Faces &gt; Click to Name


These tagged photos then show up when selecting a Person from the People Album in iCloud Photos, just as if they had been recognized by the ML algorithms.
How can I similarly manually tag People/Faces in a photo from the iOS Photos app?
In iOS 14 and earlier, you cannot manually add a face tag on on iOS. This function is only available on macOS.