Where to start to learn drawing online
Since you're interested in learning drawing without a specific medium, I recommend Udemy. It has a lot of great lessons, if you're willing to pay (~$15). My recommendation is https://www.udemy.com/course/the-ultimate-drawing-course-beginner-to-advanced/. Not only is the course long and comprehensive, but you can even ask the teacher questions about anything. He gives out assignments and reviews your submissions. You can see what other people submitted, too!

Note: I'm not sponsored in any way by Udemy or the course teacher. I took the course last year, and really enjoyed it.