On a whim I signed myself up to Data Science Math Skills from a couple of professors at Duke University (on Coursera).
This is pitched at people with little or no maths education, and so far it’s a refresh of things I had forgotten I knew around basic set and number theory. Scanning ahead I can see it’s all things I have learned once in my life, but sometimes a very long time ago (e.g. at school).
The delivery format seems to be a set of video lectures accompanied by written summaries of the key concepts. So far (presumably because these concepts were already in my head, albeit buried below the clay of decades) I’ve found that reading through the notes is a quicker way of grasping what is going on, but so far other than revision quizzes haven’t really had to test whether the ideas have stuck.
Fun to do something different!