Besides some of the very, very obvious (don’t copy/paste 100 lines of code, make it a function! Write comments for your future self who has forgotten this codebase 3 years from now!), I’m not sure how to write clean, efficient code that follows good practices.
In other words, I’m always privating my repos because I’m not sure if I’m doing some horrible beginner inefficiency/bad practice where I should be embarrassed for having written it, let alone for letting other people see it. Aside from https://refactoring.guru, where should I be learning and what should I be learning?
Well that’s something not to do. Make you “horrible code” public, and ask people to do a code review. Or see what contributors want to change through a PR (if you’re so lucky). You’re not going to learn anything from others by hiding your mistakes. And no one besides you really cares if you’re committing horrible code.
It’s pretty hard to just give generic advice on how to write clean code, but if people can just tell specifically what you can improve it’s much easier