I am on Intellij Ultimate 2021.3 Beta but my Kotlin compiler is outdated. It is bundled so I can't uninstall and install, how do I get latest one?

IDEA 2021.3 doesn't have a Kotlin plugin with 1.6 compiler yet. The general problem is tracked in https://youtrack.jetbrains.com/issue/KTIJ-18848

Hello! Kotlin plugin 1.6.10-RC for Intellij 2021.3 has been released, please try it out!