Consider adding yandex.ru and baidu.com to Default Search Engine selection for those who are not interested in using heavily censored search results from the Big Tech companies.
Firefox does have some regional search contracts, so in certain locales Yandex is the default search engine and in others Baidu in the default search engine. I mention contracts because Mozilla generally does not include search engines without some kind of agreement (most financial support for Firefox comes from these contracts).
Of course, you can add those search engines yourself using one of these methods:
(1) While on the search site, check whether it offers a search plugin: right-click the address bar and look for an extra item at the bottom of the menu ("Add ...")