I have an iPhone 11 Pro that I back-up regularly both to macOS and manually to windows (by copying the ###APPLE folders).
This phone is now full and I must delete older photos. Ideally I'd just delete the older ###APPLE folders but I believe this will mess the phone up.
I don't use iCloud since Google Photos is free and I also backup there for a worst case cloud scenario.
So how do I mass delete photos from the phone without messing it up to free up some space?