Jenkins plugins use a custom version of the gmaven-plugin that hasn't been updated in years.

There is a gmavenplus-plugin that is maintained and is Java 11 compatible.

https://github.com/groovy/GMavenPlus

The pipeline-model-definition plugin recently switched to using gmavenplus with only some additional spotbugs issues.

Jenkins parent-pom should switch to gmavenplus and exclude gmaven.