"Ecosia results and advertisements are provided by multiple search partners like Microsoft Bing and Google"

https://ecosia.helpscoutdocs.com/article/579-search-results-providers

As are most of the alternative search engines. I've been alternating between Mojeek and Brave, which each generate their own index;

Mojeek: https://www.mojeek.com/about/why-mojeek

Brave: https://dkb.blog/p/brave-search-interview

... and as a backup, DDG, which draws on Bing and a range of other sources;

https://duckduckgo.com/duckduckgo-help-pages/results/sources

#search