as Lithuania - this is absolutely not true. Even before Soviet union the Russian empire was exterminating language to the point where there's an entire Lithuanian history chapter on Lithuanian book smugglers: https://en.wikipedia.org/wiki/Lithuanian_book_smugglers

Soviet empire wasn't better either. My great grandmother who was a Lithuanian language teacher was sent to Siberian gulags _for_ teaching Lithuanian. Luckily she survived and lived to a 100 just to prove these disgusting people wrong.