The final push to start using Firefox over Chrome on Android might finally be thanks to the enormous selection of add-ons (Firefox's version of extensions) coming out next month. Chrome doesn't offer native support for extensions in its mobile app. Also, better security.
This exists already, it's called Searxng. The instances don't federate with each other necessarily but rather with actual search engines. But each instance of searxng is hosted by a different person. and so you might notice different resaults on one server vs the next. https://searx.space/