Edit: in essence it search works for searching for a community, but not an instance as a whole; I couldn’t just search wefwef.app for mander.xyz and see all of its communities listed, but I can search for a community from it and it will come up
This will show you the posts from mander.xyz as if you’re on that instance
Though I think these will leave not signed into your lemmy.world account, so I guess find the communities you like the look of and search it from your normal wefwef.app instance