Since COVID19 has made schools go online, post good self learning resources from universities and other sources that became recently became free to use.
Here are a few I have found:
https://blog.coursera.org/coursera-together-free-online-learning-during-covid-19/
https://link.springer.com/book/10.1007/978-3-319-11080-6 (free until the end of July)
https://www.pluralsight.com