This might not be exactly what you’re looking for, but I read the “big nerd ranch guide to iOS programming” which was a really great book for learning iOS devel

This might not be exactly what you’re looking for, but I read the “big nerd ranch guide to iOS programming” which was a really great book for learning iOS development. I then built an app for iOS and found that bringing it to macOS was very simple using catalyst. Mac now makes up 1/3 of my (very tiny) revenue. So, that might be one way for you to go, with the added benefit that you’ll know how to build iOS apps as well as Mac apps.