What true Open Source Software means from my perspective in the industry and how I recommend contributing to it to get your foot in the door (spoiler: it's not what most bootcamps do)

I would start with your skills and try to find more consumer products built on that language rather than the core frameworks themselves. For example, Material UI (MUI) is a great and approachable project if you are good in React, rather than trying to contribute to React itself. Another tip is to start with bug fixes or "issues" that they need help with! Always read the contribution guide first and follow the rules for submitting a proper PR.