I would recommend working through Google's Codelabs if you wanna learn Android Programming with Kotlin. They are split up in Basic and Advanced.
Re:Kotlin 1.4
by thecupisblue on Tuesday August 18, 2020 @10:10AM
(#24198733)
I would recommend skipping anything google recommended and finding courses made by people with real android development experience.
Google has it's own way of doing things - boilerplate, overengineered and full of ugly practices. Anyone will be better of learning from a source that isn't a bunch of interns that got thrown into the Android team.
Kotlin Bootcamp for Programmers[0]
Developing Android Apps with Kotlin[1]
There's also an advanced android development course which is a follow up which I am going through now.
[0] https://www.udacity.com/course/developing-android-apps-with-...
[1] https://www.udacity.com/course/developing-android-apps-with-...