Khan Academy is excellent for Calculus however their material for Differential Equations is rather minimal since they don't really go into university level mate

Khan Academy is excellent for Calculus however their material for Differential Equations is rather minimal since they don't really go into university level material. Perusing online resources for Differential Equations shows that there doesn't seem to be much agreement on how to define the core subject, and there is no grounding on 'how we got here' to provide a path forward to people just starting out. My experience so far, at least.