3 points
There are only like 4 actual search indexes online (Google, Bing, Yandex, and I can’t remember the 4th), and every other search engine just uses one or more of those for results.
1 point
I think Baidu, Qwant, Mojeek & Brave all use fully independent indices, but there are likely more. This is excliding eg. Kagi who use a combination of their own and other indices.
1 point
stract.com has their own indexer, fully open-source.
-2 points