But it doesn’t undermine the purpose of end to end encryption? End to end encryption means it’s encrypted on one end and is decrypted on the other end, as opposed to being decrypted somewhere in the middle.

This problem doesn’t for anything to undermine end to end encryption at all? With E2EE you still have to trust the other end. If the person who is the other end installs a plugin that reads the texts you send them, that’s not really a technology problem it’s an OpSec problem.