I created this course about Data Integration around 2 years back following delivering some complex integrations https://www.udemy.com/course/data-integration-guide/?couponC... (Link with coupon code) It brings around 300€/month, and is very much appreciated by professionals despite it not being very conventional. The reason to put it was to share some lessons learned in such projects I also published a book on Amazon (with some more detailed content) and it sells handful (sometimes more) copies every month.