Here's a few MOOCs I found. You can audit these courses for free, which means you'd have access to all the material except graded quizzes and stuff. I used MOOCs to get my GED prior to getting into uni. MOOCs are legit resources.
https://www.coursera.org/learn/chemerinsky-individual-rights?action=enroll&authMode=signup
https://www.coursera.org/learn/american-law?action=enroll
Cornell also has a law section on the constitution I used to review the constitution for the GED. Here's a link: https://www.law.cornell.edu/constitution