By default anyone can upload to a gallery but they are identified by hard-to-guess UUIDs. This makes passing galleries around SMS or any chat platform very easy but one thing I did not expect is groups forming long-lived persistent galleries. Once you have more than one or two of these they become hard to keep track of.
I am currently working on an app with optional accounts for end users to (1) keep track of multiple galleries (2) allow iPhone live photo uploading (no way to do that within Safari) and (3) allow iPhones to upload pictures with metadata which Apple strips from all Safari uploads.
Here's a demo gallery with uploading disabled:
https://shareable.photo/73f4b812-51bd-42de-99f6-c58f65b18ae1...