Dataminers were right: Battlefield 6 indeed will not have Russian language support. EA decided not only not to translate the game into Russian, but did not even include subtitles in the shooter. Information about the lack of localization is indicated on the Battlefield 6 page on Steam.
Battlefield 6 will become the first game in the series without the Russian language. All mainline Battlefield installments released by EA DICE supported localization, including interface, subtitles, and, in most cases, voice acting.
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Image source: EA