Please don’t get me wrong the GNUNet is a awesome idea but the question is easy to answer. Most applications for it are still in Alpha and a few in beta so it’s not even close to ready specially not to be used as “secure” messenger. Yes Matrix isn’t perfect yet ether, specially the client SDKs need some more love but it’s already really good and even used by Governmentes. After all they didn’t actually chose it which made me a little sad but rather took XMPP which is without any doubt the most mature of all those. As a little tip if it’s about security and not just pure freedom to you don’t use Beta or Alpha software for things like communication 