From Dec 2021:

Biden has not said outright whether he wishes to oust DeJoy, although his press secretary, Jen Psaki, has said she is “deeply troubled” by his leadership. Even so, the president lacks the authority to dismiss the postmaster general. That power rests with the #USPS Board of Governors, a nine-member panel that can remove DeJoy with a majority vote. There were three vacancies on the board when Biden took office, and he filled those with Democratic

https://www.theguardian.com/business/2021/dec/16/louis-dejoy-us-postal-service-postmaster-general-biden