Don't have to leave the JVM, already there in Scala. And Kotlin Arrow may get merged into the compiler, so Kotlin may have first class support for these language features one day...
At some point, I realized Java code tends to have many more runtime type errors (in particular, NullPointerExceptions and ClassCastExceptions) than similar C++ code (segfaults). Things like rust should be even better than C++, but that’s practical largely thanks to performance optimizations from llvm. Other than Java compatibility, I don’t see any advantage to the JVM at this point.