Brave uses its own index. It used to be supplemented with results from other engines but I believe they have now phased that out.

Brave is the best of the free options in my experience, and it supports "bangs" which let's you send your querry to a different engine (typing "how far is it to the sun !g" will pass the search to google. Duckduckgo also supports bangs), this is especially helpful for image searches (!gi for google images) since braves image search sucks dogshit 😅

Quant seemed like the second best free option in my experience. Some people don't like brave as a company for various reasons, so quant may be a good option for those folks. Its my understanding that Mozilla has worked with quant in some way, which is kinda neat.

Both have their own index making them a sustainable/viable option going forward, where meta search engines that use other engine's results are at the whim of those they fetch the results from (but may provide better results by piggybacking off a larger successful engine)

Ecosia uses the money they generate with ads to plant trees 🌿 (I think it's bing on the backend)

MetaGer is a metasearch engine focused on protecting users' privacy. Based in Germany, and hosted as a cooperation between the German NGO 'SUMA-EV - Association for Free Access to Knowledge' and the University of Hannover, the system is built on 24 small-scale web crawlers under MetaGer's own control. In September 2013, MetaGer launched MetaGer.net, an English-language version of their search engine.

Source: https://en.m.wikipedia.org/wiki/MetaGer

It currently supports the following languages/regions:

Dansk (Danmark)

Deutsch (Österreich/Schweiz/Deutschland)

English (Great Britain/Ireland/Malaysia/USA)

Español (España/México)

Suomalainen (Suomi)

Français (Canada/France)

Italiano (Italia)

Nederlands (Nederland)

Polski (Polska)

Svenska (Sverige)

Source: https://metager.org/lang

There is a TOR-hidden service too:

https://metager.org/tor

It is open source:

https://gitlab.metager.de/open-source/MetaGer

And has other useful features, for example:

[...] you can hide yourself behind our proxyserver just by opening the result anonymously? Use "OPEN ANONYMOUSLY"; this also affects the following links.

Source: https://metager.org/tips

Alternatively I use some SearxNG-instances, preferably hosted in the EU:

https://searx.space

Qwant was good until they georestricted it for no reason

Brave Search does not use Google and Bing. And why did you skip over DDG?

Try Andisearch, it was the first AI search ever and apart is one of the most private search engine which even actively protect your ID, no ads, no tracking, no logs, anonymous.

Adding as search engine in your browser

https://andisearch.com/?query=%s

Perplexity, well, is still one of the more private AI, but best to use the extension which works well and anonymous (logs only tech data), Chromium only. In Firefox you can use perplexity only as search engine from the website itself.

Kagi user here.

Bought a month to test it and then went for a year immediately afrer. I really like it!

Don't forget DuckDuckGo.