Others have already mentioned that this is possible with iOS. iOS 14 introduced a bunch of privacy improvements including the PHPickerViewController, but some apps may not yet be using it. [0]

I will say that in the event that an app is not using PHPickerViewController, sometimes it's still possible to emulate it by exiting the app, going into the photos app, selecting the photo, selecting the little "send" arrow in the bottom left, and then picking the app to send it to. I do this all the time with the Slack app. Copy-and-paste may be another route. Sure, it's a silly workaround for a feature that should have been there from day one, but c'est la vie.

[0] https://developer.apple.com/documentation/photokit/deliverin...