Do macrophages phagocytose ONLY foreign substances (only antigens)

Or do they also phagocytose common body cells (when these cells die)?

Macrophages continuously phagocytose dead cells, any kind of debris, and
old red blood cells, as well as foreign cells, like bacteria and viruses.

The difference is, when they phagocytose foreign cells, the foreign antigens are transported to the surfaces of the macrophages, and "presented" to lymphocytes.
So macrophages are antigen-presenting cells, and are critical in the initiation of the immune response.