We recently went to the exhibition "China's Hidden Century" at the British Museum https://www.britishmuseum.org/exhibitions/chinas-hidden-century, which was fascinating and, as is usually the case, language issues were very important.
The exhibition made it very clear that China was very much a multilingual society and there were recordings of texts in Mandarin, Cantonese, Manchu, Mongolian and Tibetan. This large variety of languages reflected the languages that were spoken in the Empire and Beijing, in particular, was a multilingual cosmopolitan city.
I bought Lovell's (2011) book on the opium wars to learn more about the background. At several points, she discusses language issues. She describes how the Emperors had a desire to learn languages. For example, Qianlong knew six languages and used Mongolian and Tibetan in audiences with representatives of these groups. He stated "I use their own languages and do not use an interpreter ......to conquer them with kindness" (Lovell 2011: 90). So, he saw knowledge of languages as giving power.
Not knowing languages was also seen as a way of preventing enemies or rivals from having power. The Qing did their best to prevent foreigners from learning Chinese and Manchu. This even went as far as making teaching foreigners Chinese in Canton in the early nineteenth century a capital offence (Lovell 2011).
Current politicians in the UK who do little to promote the learning and teaching of modern foreign languages could learn from the Qing Emperors.
Lovell J (2011) The Opium War London: Picador