there is Khan Academy it teaches thoroughly. sometimes too long. for just short explanation and move on. it really teaches. however because it is too long it is easy to forget what it teaches.
i wish there was a fully covering course in pre calculus and linear algebra math with method that is like https://www.hirez.io/ or https://www.youtube.com/watch?v=A5eihauRQvo/ i discovered they like generate dopamine every 30 seconds. the information is concentrated. any humming or waiting is cut out. probably what generates dopamine is audience’s preoccupations and life sustaining desires (like food and beautiful someone of opposite sex), abundance and patterns like music. maybe also with adrenaline (something that might be fearful, maybe not scary later)