My professor is not teaching his online course himself, but uses publicly available videos instead. Is this appropriate?
If your instructor is available for questions, comments and discussions, then you can learn a great deal this way, potentially.

I recommend that you try to do just that.  If, after at least ten days of really trying, you have difficulties, or find yourself concerned that you may not be properly prepared for courses that build on the one you're currently taking, then I recommend that you reach out to a department administrator.  Present it as a problem you are having, not as a problem your instructor is having.  However, do lay out in as neutral a tone as possible, a description of the current course format, and if your instructor has been unresponsive to questions, do include that information.  Draft the email and sleep on it.  The next day be brutal and remove any trace of whining or complaining.  Just state the problem as a problem you are having.

Hopefully you will not have a problem.

Happy studying!