If it's integration with R you're after, I think you should seriously consider C++. The Rcpp package gives R fantastic support for C++ code (either compiled on-the-fly or beforehand), and it's the engine by which a lot of R code is optimised.
The other languages I'm less familiar with, unfortunately. Kotlin looks interesting to me, but I don't know how much it's being used outside of Android development (not saying that rhetorically—I haven't looked into it enough!). Java I'm not quite ready to go back to (I did it and C++ when I was younger; I wish I'd started with a fun language like Python or R
), but for sheer ubiquity in enterprise settings you can't beat it! Scala I'm absolutely clueless about, sorry 
One weird side note as someone else who's into R and has been working on the JS side lately: I've been holding a torch for game development since high school, and the Unity engine always interested me because it supported both C# and a weird flavour of JS. I'd intended to play with it using that JS flavour, but I wasn't thrilled with it. If you have R and JS datavis skills and wanted to take those in a different, less data engineering focused direction, you could learn C# and tinker with pushing data into Unity.