Best Free and Open Source Alternatives to Autodesk EAGLE

Autodesk EAGLE is available for Linux, but it’s proprietary software. What are the best free and open source alternatives to Autodesk EAGLE?

EAGLE is a scriptable electronic design automation (EDA) application with schematic capture, printed circuit board (PCB) layout, auto-router, and computer-aided manufacturing (CAM) features. Several open source alternatives are available to Linux users. Learn more here.