Did some more research on this... looked deeper into setup requirements of Pleroma/Soapbox and wasn't super convinced for various reasons (but it is not totally off the list). Also explored Misskey, but while it looks nice, it isn't quite what I am looking for.
In the end I am currently tending towards Pixelfed. While that is "photo" focused it would probably also work well to share game screenshots and short videos/gifs, which is what our Hubzilla was mostly used for. Also has build in creative commons licensing support, which is nice for sharing 2D game art. Only problem right now: semi-broken postgresql support :(
Edit: Ok I ordered some new SSD storage for another server and will likely transfer the IRC server and Pixelfed on to that one, as both require a MySQL/MariaDB database for full functionality, which I don't really want to install on the current server (which runs a Postgres database). This other server is a bit slower, but I think it will be fast enough.