This XSeries on edX [0] looks promising for some of the prerequisite knowledge. Then for PCB design specifically, there are specialty courses on Udemy, for example, "KiCad Like a Pro" [1].

[0] https://www.edx.org/xseries/mitx-circuits-and-electronics

[1] https://www.udemy.com/course/kicad-like-a-pro-3e/