I've created lots of content to augment existing courses, and I teach online course developed by others. It's getting to be about time I construct my own course from start to finish.
The website Teachable would be a way to do it outside of my institution. Canvas could also handle it, although I don't think they're set up to promote, register, and sell courses they way Teachable is.
However, I use Canvas both with my private students and the kids at Joliet Junior College, so I could certainly use any course I create on that platform with my existing clients. But perhaps I could not easily sell it to the outside world.