Anyone from JetBrains working on Mutation Testing tool for Kotlin based on IR instead of JVM ByteCode? Which is the right forum to discuss this in more details?

Not sure, but you might ask #kotest https://github.com/kotest/kotest/blob/master/doc/plugins.md#pitest Also @hjc might have some ideas https://github.com/pitest/pitest-kotlin

pitest works at JVM bytecode level