Is there any messenger that does end-to-end encryption with reliable, in-order delivery with decentralized group chat and conversation history syncing? Been looking for years but so far the double-ratchet is inadequate.
Mumble / Murmur are close to this, but without chat history syncing. End-To-End PFS encryption though. Very decentralized, but you can tie it into ldap and other authentication systems. I linked in another part of this thread.