Not sure it’s the right patch though. (Does a search engine need an extension to support being used for omnibox search? It might.) In any case, the two ultimate sources of the linked report seem to be:
Grigory Bakunov[1] (ex-Yandex) observes Yandex has been removed (but e.g. OZON is still there): https://t.me/addmeto/4782 (ru, but basically amounts to a screenshot)
Mozilla posts a vague note saying the “default search engine” (NB: omnibox default, not just installation default) may change in Firefox 98, no specific engines are named: https://support.mozilla.org/en-US/kb/search-engine-removal (en)