Ask HN: Free resources to practice Product Management outside of work?

I’m working at a dead end job with no paths to shift to a product management roles. It’s also a tough market for jobs and I’m looking to develop PM skills for the future. I currently volunteer as a product owner at an NGO for a few hours a week but I’m looking for more resources that can help me fill gaps in my PM experiences so I can learn more and inadvertently stand out in my resume.