oh, seems there was a hardware vector, just not on motherboards https://www.commerce.gov/news/press-releases/2018/10/addition-fujian-jinhua-integrated-circuit-company-ltd-jinhua-entity-list Effective October 30, 2018, the Department of Commerce has taken action to restrict exports to Fujian Jinhua Integrated Circuit Company, Ltd. (Jinhua) by adding them to the Entity List (Supplement No. 4 to Part 744 of the Export Administration Regulations (EAR)), because Jinhua poses a significant risk of becoming involved in activities that are contrary to the national security interests of the United States.

Fun times