How about Emacs Org-Mode? :P
It's worth noting that it has a TUI mode, unlike the tools above, so even problems with a graphic server or connecting to the machine via SSH are not an obstacle for making and accessing quick notes. Surely most of the tools use some plain text format underneath which can be viewed and edited by arbitrary tools, but having a reliable plain-text first format is better for the matter.
I'm afraid it won't work unfortunately. The "Metaverse" is essentially a brand name of former Facebook already, they would spend a lot of resources into promoting it, and they wouldn't interoperate with external implementations for sure. It's pretty clear they have big plans for it, that's why they announced a few years ago that Oculus Rift would become non-functional for those who don't have a Facebook account, for example.
So, naming anything else a "metaverse" is just the same evil as "googling" in other search engines than Google: regardless of the intent, it still strengthens the monopoly and the belief that Google is *the* search engine, and others just stay in its shadow. It's better to avoid calling alternative virtual worlds a "metaverse" and come up with some independent branding for the open ecosystem instead, to highlight the supremacy over the Meta's attempt, rather than the opposite.