What is known as servers on Discord also exists on Matrix. They are called spaces and you don’t need to self-host a Matrix server to create a space. There’s also no significant learning curve, you just download Element (the most popular Matrix client), create an account and you ready to go. You can join spaces or groups from any Matrix server or message anyone on the network. Chats also make use of end-to-end encryption by default and it can even be activated for groups (wouldn’t make much sense for public groups though).