To sum up my experience: Scala can be even more terse than Kotlin, but I found Scala code generally harder to read and understand compared to Java. It has the kitchen sink thrown in in terms of features and the idiomatic way of writing code is pretty complex and very different from Java.
Kotlin on the other hand is just a breath of fresh air, very easy to pick up and get productive.
I just hope they keep the language to a manageable size and don't keep putting things on top.
Haven't tried the Ergodox, but had bad experiences with thumb keys on both a Kinesis Advantage and a Keyboardio.
Then I tried the ultimate hacking keyboard and I absolutely love it, especially the mouse emulation layer. And it took me way less to get used to it compared to the above two. I can't recommend it enough!
Kotlin on the other hand is just a breath of fresh air, very easy to pick up and get productive.
I just hope they keep the language to a manageable size and don't keep putting things on top.