The Clojure language is bootstrapped on GNU Guix.
Clojure just did the right thing regarding bootstrappability. They have a bootstrappable build system (Ant), and they have their core in a bootstrappable language (Java), that is just enough to build the parts of the Clojure complier so that it can build its Clojure files.
The Groovy language is bootstrapped on GNU Guix. Just like Clojure, Groovy has a core written in Java that is just enough to build the parts of the Groovy compiler. Unfortunately, Groovy relies on a Gradle build by default, which in turns relies on Groovy as its build description language.
We do not know about a bootsrap path for Scala. Going down the dependency chain of Scala proved to be futile, as the first pulished version of Scala depends on proprietary software. Most probably the only way to do this, after a thoughtful mapping of problem space, seems to be writing a bootstrap compiler for Scala. Some preliminary work has already been done in that direction, but it is not ready for publication yet. People interested bootstrapping Scala are welcome to inquire on the #bootstrappable IRC channel on freenode.
We do not know about a bootstrap path for Kotiln. We are in the phase of mapping the dependencies of Kotlin to get a plan to have it bootstrapped. People interested in bootstrapping Kotlin are welcome to join in.