Generally, I prefer books and self-education to courses, but here are a few that I enjoyed:
“Learn the basics of Assembly 6502 and computer architecture programming games for the Nintendo Entertainment System”
NES Programming with 6502 Assembly
Handmade Hero is an ongoing project by Casey Muratori to create a complete, professional-quality game accompanied by videos that explain every single line of its source code.
This series is designed for programmers who know how to write programs, but don’t know how hardware runs those programs.