I started Koans (and will still finish them) but the bugs were eating up enough time it's distracting me from learning, lol

the docs are pretty good for java devs https://kotlinlang.org/docs/reference/

Notice there is a "Migrating from Java" tab at that link that may be helpful to you. Udemy has a number of ~$10 Kotlin courses, you may be able to find one that has at least some content that fits your needs.

Sweet! Thanks!!!

Recently, there was also this codelab released https://codelabs.developers.google.com/codelabs/java-to-kotlin/