But instead it offers people to learn hosting and sysadmin stuff.
It does not. The post says paying for a hosted matrix server. That means you pay for somebody to host it. There's nothing more to it.
The full discord nitro plan costs 10$/month. That can get you a server for your friends and you can communicate with other servers. If everybody chips in, it's the cost of discord nitro minimum if you're 5 friends.