Hey, could you post the link of the channel you mean? Looking for 'shadertoy' in Youtube brought me only a playlist by 'The Art of Code'. Is that the channel you mean?
https://www.youtube.com/watch?v=0ifChJ0nJfM is probably the the most beginner friendly.
https://thebookofshaders.com/ is another great place to start.
Good luck and enjoy!
EDIT: here are the links as promised.
1. https://thebookofshaders.com/ (mentioned above, I think)
2. https://threejs.org/docs/ (of course)
3. https://docs.pmnd.rs/react-three-fiber/getting-started/intro... (optional; good for React and those comfortable for maybe don't dive right in until you get a good grasp on Three.js)
4. https://threejs-journey.com/ (a paid course with some good intro lessons as freebies)
Hope this helps!
Also, threejs journey is worth it. Lots of great content.