My progression into open source is documented in an interview (link below), but in short by running Debian, contributing to Debian packages I use and other packages, following Debian mailing list discussions, Debian community blog posts and IRC channels etc. The same probably applies to other FLOSS distros too. For a while I noted down a list of interesting software, but the open source world has exploded since I started that list so I stopped maintaining it. Also reading HN often brings up new open source projects I didn't hear of yet.

https://zgrimshell.github.io/posts/interviews-with-floss-dev... https://bonedaddy.net/pabs3/about/#interviews https://wiki.debian.org/PaulWise/InterestingSoftware