I gave you the answer that exists: I'm not aware of any existing or likely-to-exist secure messaging solution that would be a viable recommendation.

The available open-source options come nowhere close to the messaging security that Signal/Whatsapp provide. So you're left with either "find a way to access Signal after they pull out of whatever region has criminalized them operating with a backdoor on comms" or "pick any option that doesn't actually have strong messaging security".