This is no surprise. During his tenure in the Trump administration, former White House counsel Stephen Miller was a prime architect of the president’s hardline immigration policies, including restrictions on asylum applications, efforts to limit legal immigration, an expansion of detentions, and separation of families. He is also thought to have been the main proponent of the travel ban on citizens of many majority-Muslim countries, and was an advocate of policies to dramatically reduce the refugee intake of the United States, among other initiatives.
It has also been reported that one of his ideas was to strip Palestinians living in areas occupied by Israel of their right to reside there, with his broad goal being to deport them from the region altogether.
However, due to internal opposition in the Trump administration, this policy never came to fruition, and no such orders appear to have been issued. Furthermore, it is highly unlikely that Miller will be able to pursue his policy objectives in the Biden administration.