Combating Loneliness Act This bill creates and expands programs that promote mental health to address loneliness and that support the mental and community health workforce. The bill creates grant programs that address loneliness by supporting community facilities (e.g., parks) and community outreach to at-risk individuals. It also expands grants promoting healthy lifestyles for older individuals to include services addressing loneliness. In addition, the bill expands Medicare and Medicaid to include services provided by community health workers and increases the Medicaid federal matching rate for these services. It also expands Medicare to include certified community behavioral health clinic services. The bill provides statutory authority for grants for developing school-based mental health programs and services. It also establishes grants for partnerships between certain entities, such as between hospitals and schools, to coordinate group therapy for mental health. The bill reauthorizes through FY2029 the 21st Century Community Learning Centers program and expands it to include mental health services and community service. It also reauthorizes for FY2026 grants for health care services in schools provided under Medicaid or the Children’s Health Insurance Program (CHIP). The bill establishes a program for repaying student loans for individuals providing mental health services in designated shortage areas. It also makes community health workers eligible for the National Health Service Corps’ federal loan repayment program. Additionally, the bill reauthorizes through FY2029 grant programs supporting full-service community schools, substance abuse recovery, and mental health for the health care workforce. It also requires a Government Accountability Office study on social isolation.