It will be open source, end to end encrypted using Signal’s double ratchet encryption protocol, and he plans to make it easy for fediverse platforms to integrate it. The beta will release later this month.
He’s also the creator of https://fedidb.org btw
I don’t think this could convince the rest of the family to switch off Line, but I’m pulling for it.
I don’t think it would work if it was offline, would it? /s