As a professional, I couldn’t do my work without open source. I use and depend on open source stuff for pretty much anything I do professionally. I tend to prefer open source as a generally more future proof way of doing things and avoid proprietary solutions.
All the development tools I use are open source and all the libraries I depend on are open source. Sadly, being a contributor is mostly not in scope for my day job and I find I like to do other stuff than coding in my spare time mostly.
Nevertheless, I have a GitHub account with the following projects and forks: