I'd flip that around and say that server-side chat history, large group chats and multiple clients are hard to implement in the context of an E2EE chat service.

I'd flip that around and say that server-side chat history, large group chats and multiple clients are hard to implement in the context of an E2EE chat service. What I mean by that is: E2EE is a necessity, not some nice-to-have feature. Building a chat service with server-side chat history but without E2EE is like building a car with very nice headlights that doesn't actually move.