I’ve had better results searching through the instances themselves because Google doesn’t always index the keywords on time. On caveat of this method is that if the instance doesn’t have the syncing out the instance where the info is from being propagated, then this trick would not work
Thanks to your post I’ve noticed that just typing the following string while using a search engine (Google in this case) we can get all of wikis that use MediaWiki that are indexed because they follow the same URL structure:
site:*.*/wiki/Main_Page