Yandex and Mail.ru have been removed as optional search providers in the drop-down search menu in Firefox. - eviltoast

If you previously installed a customized version of Firefox with Yandex or Mail.ru, offered through partner distribution channels, this release removes those customizations, including add-ons and default bookmarks. Where applicable, your browser will revert back to default settings, as offered by Mozilla. All other releases of Firefox remain unaffected by the change.

Bugzilla: 1759009 - Update Distribution Config

lemmy.ml: Firefox v98.0.1 removed Yandex search option and used misleading bug name to hide it

Hacker News: Firefox removed Yandex search option