Usually the open source community is very scattered, there are many groups developing similar projects like operating systems for instance. If all open source developers focused on the same system it would be miles ahead of the proprietary alternative but it’s usually the other way around. I think with the Metaverse is important that we focus early on a single project because if the Metaverse gains traction everyone may end up living in Facebook’s virtual reality and that would be the same as if we considered Mark Zuckerberg to be our god.
There is also
http://opensimulator.org/wiki/Main_Page
https://hubs.mozilla.com
s FOSS privacy alternatives