I somewhat-recently setup a Matrix, Element, and Jitsi server to use with a friend of mine. It's awesome having this self-hosted, federated, and E2E-encrypted chat. Matrix is not just about direct messaging one or two people, though. Matrix also has rooms, their version of Discord servers. Furthermore, you can use it as an IRC client/bouncer. So far, I have had excellent experiences.
Compared to other platforms (Discord especially), people in Matrix/IRC rooms are far more willing to help (and usually more knowledgeable). I made a toot about it, but I'll go more in-depth here. On a NixOS server of mine, I decided I might as well install Wireguard to have an extra VPN at my disposal. Users (rightly) frequently complain of sparse NixOS documentation. It has nowhere near the userbase of something like Arch or Debian, and thus much less official documentation and user experience. Regardless, I did find a few pages on how to setup Wireguard (of course, they had some major differences so I still did not know the best way to implement it!). Eventually through some tinkering, I got a configuration and I successfully connected to my NixOS server. I could access it and what was locally on it, but I realized I could not reach the internet. I tried a bunch of different fixes, and initially thought my "client" config was incorrect, but with almost every config I found, mine looked the same. I decided to pose the question in the Matrix/IRC channel and a user was extremely helpful and responsive. They guided me through different diagnosis techniques and even helped explain a few concepts. In the end, we realized the network interface was an "unusual" name, so the standard example configs would not work. I'm sure similar experiences can be found on other platforms, but this attitude is far more prevalent on Matrix/IRC.
True Casual Conversation🔗
Another element (no pun intended) I love about Matrix/IRC rooms is the "off-topic" rooms where somewhat-related (sometimes not at all) casual conversation occurs. Online communities/forums are always nice to participate in (if there is good content), but they are frequently absent of so-called "casual" conversation. Plus, as these are "off-topic" rooms of some main room, there is an inherent common interest. I have had and witnessed many more good-faith conversations and discussions than any other social platform (maybe besides the Fediverse).
The GrapheneOS Matrix/IRC is also filled with extremely knowledgeable people (cough Daniel Micay cough). As the channel is publicly logged, it is an invaluable resource for mobile security/privacy information. For instance, search "Titan M", and you will find numerous conversations on the topic (with links, too).
Many other IRC channels (you can just search through a Matrix room) are also logged, such as the many NixOS channels. The same thing applies, this resource is invaluable for finding more NixOS information. Especially with the aforementioned lack of documentation. For example, if someone searched "Wireguard", they would find my troubleshooting conversation (among other Wireguard conversations, of course), and can apply the same diagnosis methods.
Federation, Decentralization, and Secure🔗
This is more Matrix-specific, but perhaps the most important. Matrix is a decentralized and federated protocol, so anyone can use their own home-server and talk to others on different servers (similar to ActivityPub). This means no single entity controls the entire network.1 Additionally, Matrix uses end-to-end encryption, so your chats are secure, even from the homeserver, making it a viable replacement (as long as the users are technically-inclined enough)2 for other secure messengers. The best thing that can happen to Matrix is simplifying the experience, and then we will have a truly decentralized/federated secure messaging system that anyone can use.
 Although, the Matrix team controls
matrix.org, which many users by default sign-up on. This is a centralization issue, but hopefully users explore other homeservers.
 If you want some practice, message me at @jacob:matrix.jnep.xyz