How to SEO someone courses.

Valuable advice are invited on how to do seo on some courses sites like udemy, upgrade etc.

There are lot of blogs available in google, You need to find and learn your self that will be good for you

Use parasites properly you can drive a lot of traffic from them.
I would suggest make a great course introduction video on YT.
Create as many high DA contextual properties embedding your YT video.
I don't think you need to worry much about SEO because those websites already have authority.
But you should focus on optimizing your course landing page content.

Hope this helps you!