I started taking graduate matsci courses several years ago at the UW via the Edge program, and also took some on campus. I have found it hard to continue though as the UW materials science school doesn’t have a deep schedule, and they have decommitted from the distance learning effort. So I am shopping for other programs.
Columbia’s program — CVN - Columbia Video Network — seems to be among the most complete with a full schedule of courses. And they offer a full MS degree via online. And you can start as a non-matriculated student. Florida has a program as well. And so does USC, tho the courses offered is a smaller slate than Columbia’s.