If the app is open source (or at least the source code is accessible), the user would proceed to the source repo, clone it, open the Xcode project and relink to the framework version of their choice.
Others have pointed out how it could work with closed source apps. It's a bit more complicated, but it certainly is possible.
Others have pointed out how it could work with closed source apps. It's a bit more complicated, but it certainly is possible.