Not sure what the problem with Gajim was. There's a distro package already in Arch, although I usually use the AUR packages from git. I haven't had any problem with either of them, though.

You should be able to limit MUCs so that they're only for local users of a server and not accessible to people outside the server. Or, you can make them invite only, require a password, etc. So there are options there.

One-to-one video and audio chat works pretty well with XMPP. I don't think group video/audio works, but I've never tried. I know that's a really popular thing on Discord, so it'd be nice if XMPP had that too. I think there's some work toward it, but I don't know where that's at.

You say that XMPP is much lighter. But I think that is mostly due to Synapse not being very efficient. Other implementations are fairly light. Even then my Synapse is using fairly small amounts of resources. You should also check that you are making an apples-to-apples comparison with large rooms, media and message history like you would typically see in a common Matrix server.

I have a Prosody server running with about 10 concurrent users (friends/family). I just checked and it's using 32M of RAM, local storage is in the megabytes. The database I'm using as a backend for message history and such is about 70MB. The only other data is temporary cache for uploaded media, which varies depending on what's uploaded. How does that compare with a typical Matrix server for friends and family?

I couldn’t find any decent XMPP clients that supported encryption and worked on both desktop and mobile without looking like they were made in 1995

For Linux and Windows, gajim works very well and is easy to use. It definitely doesn't have an interface from 1995. If you need something easier for people on Linux, dino is even more streamlined and is extremely easy to use. I think there was an effort to make a Windows build too, but I don't know how far along that is or if they are still working on it.

For Android Conversations is the gold standard. On macOS there's Sikin and Monal, but I've never used them since I'm not a Mac or iPhone user. But all these clients support a wide variety of features including encryption.

It also doesn’t seem to function well as a Discord-like replacement, since I don’t want a separate “group chat” for every single topic. I want a central hub where people can then join pre-existing channels like you can in Discord and Matrix.

I'm not sure I follow you on this point. XMPP has had MUCs (Multi-user Conferences) which function similarly to chat rooms/IRC channels for a long, long time. The channels are accessible regardless of what server you're on as long as your server is federating with the wider XMPP network. There's even a searchable list of public MUCs at search.jabber.network covering a variety of topics. Most servers allow creating new channels if you want to start a new one, and anyone can join regardless of their server.

I've been an XMPP user for decades. I use it daily to talk to all of my friends and most of my immediate family, so I'm certainly an advocate for it.

I think in the simplest terms Matrix gets mentioned more often because it's newer and it's development has largely been driven by a corporation with significant funding. XMPP had similar corporate sponsors years ago, but a lot of them moved on. The XMPP community isn't gone, though, and XMPP development has continued.

As others have said, it's true that XMPP had some difficult issues in the past with various clients only supporting certain extensions (XEPs), which meant what worked on one client may not work on another. This problem isn't nearly as much of an issue nowadays, but it was frustrating in the past. There are official compliance suites that clients and servers can use to ensure they meet the base features for a particular purpose, so that has helped in that regard.

To me, XMPP is preferable because it's a messaging protocol, not a giant graph database of all social interactions. I don't need or want that. The main XMPP server software does handle message history that is synced across all devices, but this is often user configurable and none of that information is needed by or shared with other servers. MUCs are not replicated across the network, but only exist on the server that hosts them. While this does mean that server is a single point of failure, it's much simpler to operate and, at least in my opinion, is better from a privacy perspective.

Traditionally XMPP, albeit with propriety extensions, has been used as the basis for a large number of messaging platforms. Google Talk was XMPP. Facebook Messenger was XMPP. WhatsApp still is XMPP, as far as I know. Kik is also XMPP. Google and Facebook's platforms may still use XMPP, but I don't know for sure. It certainly works as a messaging platform for lots of users, but without all the VC money, development is pretty much only done by volunteers or client developers that offer paid builds of their clients (like Conversations on Android).

Okay, fair enough. I do agree it's ambiguous, but I don't draw the same conclusion.

Is that because you don't accept what Todd Howard and Christopher Nolan said about the timeline?

I think it's somewhat ambiguous. It lists the fall as 2277, but then there's an arrow to the mushroom cloud. So it doesn't say it was nuked in 2277, but it doesn't actually say when the nuke occurred either. But Todd Howard says New Vegas is canon and the nuke came after, so that pretty much answers the question, doesn't it?

IGN had an interview with Todd Howard and brought up the confusion and he said the events of New Vegas are canon and that Shady Sands was bombed after 2281. The sign outside Shady Sands in the series also refers to it as the first capital of the NCR, which would imply there's at least one other.

https://www.ign.com/articles/fallout-official-timeline-confirmed-how-the-show-fits-in-with-the-games

If you haven't already, you can try the MUC search at https://search.jabber.network.

It looks like everything is operational and federating with the wider network at this time. Hooray!