That error also happened here: /e/ OS “easy” installer: development thread about adding new devices - #15 by andrelam
But there is no hint in that topic how to resolve this.
One idea: check the settings for Gradle in IntelliJ. For me it looks like this
Edit: according to https://stackoverflow.com/a/62130653/6309275 that message points to the wrong Java version. 52.0 as class version means, IntelliJ is either using Java 8 or a higher version of the Java SDK that is configured to only allow Java 8 features.
Anyway, I’d first check the settings from above screenshot. Sounds a bit like the wrong Gradle JVM could be the issue.