Robert C. Byrd Mine Safety Protection Act of 2020 This bill revises requirements governing (1) investigations of mine accidents, (2) miners' rights and protections (e.g., whistle-blower rights and protections), (3) mine health and safety standards, (4) underground coal mines, and (5) health and safety training for miners. The Department of Labor, when investigating coal or other mines, must (1) determine why an accident occurred and whether there were violations of law, mandatory health and safety standards, or other requirements; and (2) make recommendations to avoid a recurrence of an accident. The bill expands Labor's enforcement authority, including by requiring Labor to (1) revoke the approval of mine operators' plans or programs based on certain criteria, and (2) order mine operators to withdraw all persons from a mine until Labor approves a new plan. The bill revises civil and criminal penalties, including by subjecting a mine operator who knowingly violates health or safety standards to a felony punishable by up to five years in prison and a $1 million fine. Underground coal mine operators must implement a communication program to brief miners of current mine conditions and install atmospheric monitoring systems. The bill amends the Occupational Safety and Health Act of 1970 to expand its coverage to government employees and increase civil and criminal penalties for violations of the act. The bill also expands whistle-blower rights and protections against retaliation under the act, establishes employee rights with respect to work-related bodily injuries or death, and establishes procedures for correcting serious, willful, or repeated violations of occupational safety and health standards.