IRC is a simple interface that's been well supported for more than two decades, folks have a huge selection of apps or web interfaces they can choose from. No it doesn't directly support sharing pictures or anything like that, but for most chats all you need is basic text. It's easy to build up a quick bot in several different programming languages and I've even written up self-running multiplayer games.

I considered switching to something like discord for the chats I host but it didn't look like they allow that although there are some open source alternatives. What's the deal with Matrix? Is there a reason you like it better? Can you easily set up a self-hosted server for it? (And for that matter, are there any connectors to link it to an existing IRC chat to allow for a smooth transition period?)