One of our instructors at CSU does his entire course web site using
Pmwiki, which uses a markup language. If you follow certain conventions, it can be converted to a slide show in the browser. For an example how this works, see https://www.cs.colostate.edu/~cs253/Spring19/ This is a C++ course for students in the second year. On the home page is a link to the slide technology used. I believe it is java script that takes the HTML file and renders it in a slide format. If you look at the Schedule page and click any of the links to lecture material, you will see a straight web page. At the top left corner is a link that will render the page as a slide show. You can advance through the slide show using the arrow keys.
One of the other instructors takes screen shots of the PowerPoint slides and embed them in the HTML page. For an example of this style, see here.
If either of these interest you, I can put you in touch with the specific instructors.