Why did the Qing dynasty prohibit Han Chinese from entering the northeast?

There are several reasons why the Qing dynasty banned Han Chinese from entering the northeast:

First, the Northeast is the birthplace of the Qing Dynasty, and the entry of Han people into the Northeast will affect the foundation of the Qing Dynasty. If the Qing Dynasty could not rule the Central Plains, it could still return to the Northeast, which was their base. If the Han people enter the northeast, not only the customs of the Han people enter the northeast, but also the influence of the Han people and even the anti-Qing armed forces may enter the northeast. Assuming that their rule in the Central Plains fails, they may not be able to keep the Northeast. So, they thought of a move to ban Han people from entering the northeast.

Second, the Qing dynasty was afraid of the shrewdness and culture of the Han people. For the Qing dynasty, although the Han people were ruled by them, their shrewdness and culture were better than that of Manchu. The reason why the Qing Dynasty was able to rule the Han people was mainly due to the corruption of the government in the late Ming Dynasty and the powerful influence of the Qing Dynasty. However, when it comes to cultural Manchu, it is definitely behind the Han nationality. If a large number of Han Chinese enter the northeast, the northeast may not be ruled by Manchu, but will gradually be ruled by Chinese culture and even Han Chinese, just like Indonesia now.