What is a good immutable collections library?

So I have not been thrilled by kotlins read-only collections, especially when “mutating” (ie, creating a new collection with the result of the change), due to the performance issues. I miss what Scala offers in that regard.

Are there any good third party libraries for Kotlin that bridge this gap? I have seen the kotlinx one, but haven’t had time to take a close look.

Thanks.