It is Chinese.

According to historical records, Manchu still has a certain scope of application in archives, questions and answers between monarchs and ministers, and formal occasions. For example, when meeting foreign envoys during the Guangxu period, records indicate that Emperor Guangxu used Manchu to host the occasion. The original Manchu text of one of the electronic versions of rare Manchu books recently released by Harvard-Yenching Institute, the "Sino-Russian Xianfeng Eleventh Year Treaty", points out that the final interpretation of the treaty is dominated by the Manchu version. Perhaps it was not mentioned much in Chinese history circles in the past.

In short, although the scope of application of Manchu in daily life is constantly shrinking, it is not as useless in formal occasions as we think. In daily summons (i.e., imperial memorials), the language spoken by the emperor depended on the identity of the ministers and the content of the memorial. In some cases, Chinese or Manchu was used.