https://www.congress.gov/115/bills/s1804/BILLS-115s1804is.xml#toc-id25c91cb96228483495ad9de0b47b79f8
While the bill says it only prohibits supplemental plans that duplicate the Medicare4all plans, here's what would be covered and you tell me what somebody buy supplemental coverage for?
(1) Hospital services, including inpatient and outpatient hospital care, including 24-hour-a-day emergency services and inpatient prescription drugs ; (2) Ambulatory patient services ; (3) Primary and preventive services, including chronic disease management ; (4) Prescription drugs, medical devices, biological products, including outpatient prescription drugs, medical devices, and biological products ; (5) Mental health and substance abuse treatment services, including inpatient care ; (6) Laboratory and diagnostic services ; (7) Comprehensive reproductive, maternity, and newborn care ; (8) Pediatrics ; (9) Oral health, audiology, and vision services ; (10) Short-term rehabilitative and habilitative services and devices."