For disappearing messages to work, your conversation partner has to promise they won’t take photos of their screen, and they have to promise to use an app that actually implements the feature instead of just pretending to, and the app developers have to promise to have implemented the code to delete a message when the service says it should

Is there actually a cryptographically-sound and physically-complete method for ensuring that a message is only legible for a temporary duration once it leaves your own device and is delivered to someone elses?