The only one I see linked often is tilvids.com. There may be more popular ones though.
If this was to be a feature then it should be linked to the lemmy instance itself, lemmy communities shouldn’t auto create rooms on matrix.org. Also It wouldn’t make sense to add something like this unless lemmy had deeper matrix room integration even if it was barebones.
To add on to the other replies, GNOME is the simple and polished desktop experience for linux. KDE aims for features and maximum customizability with a modern desktop paradigm, XFCE aims for lightweight and classic desktop paradigms, and GNOME aims for a simple and fresh take on desktop paradigms with a focus on creating sensible defaults in place of customization.
GNOME is generally slow to adopt new features compared to KDE but when they do it’s more thought out and integrated, if that makes sense. It also has a more decisive path forward, it’s development team has a vision and actively works toward that vision despite what others might want which might be a good thing or a bad thing depending on what you expect out of your desktop experience.
It’s design is a remnant of early 2010s desktop design where touchscreens and 2in1s were the future and everyone was racing to redesign their desktop to work with both but at this point it’s the only one that succeeded and got close to that end goal
You can but you would have trouble gaining activity since the biggest attractor for new users is activity and it it would be difficult to get that initial momentum with such strict posting guidelines. If you had an established userbase though it’s a great idea.