./ktlint --format "foo/ /*.kt" "!foo/ /generated/**"

Exception in thread "main" java.util.concurrent.ExecutionException: java.lang.NoClassDefFoundError: Could not initialize class org.jetbrains.kotlin.com.intellij.openapi.util.objectTree.ThrowableInterner
at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191)
at com.pinterest.ktlint.KtlintCommandLine.parallel(Main.kt:575)
at com.pinterest.ktlint.KtlintCommandLine.parallel$default(Main.kt:547)
at com.pinterest.ktlint.KtlintCommandLine.lintFiles(Main.kt:298)
at com.pinterest.ktlint.KtlintCommandLine.run(Main.kt:262)
at com.pinterest.ktlint.Main.main(Main.kt:70)

The same command without format works (shows warnings)

0.42.1 command line, MacOS