I learned the most about linux, networks, and the internet by just getting into projects that are useful for me personally and connected to my hobbies. Self hosted projects are great for this (sftp server, torrent server, gitea, etc. https://github.com/awesome-selfhosted/awesome-selfhosted ) While this method really helps with motivation and will probably be the most fun, im also currently looking for some more systematic ways of learning things like security best practices.