It was not possible to just run 'mvn spotless:check', but instead one needed to use the fully qualified name of the plugin, i.e., 'mvn com.diffplug.spotless:spotless-maven-plugin:check'.

This is due to 'force-shading'; this module is declared as a child of the flink-parent pom (i.e., the root pom of the project), but is not actually declaring that very module as it's parent.
This seems to throw of maven, which fails to retrieve the plugin information from the parent.

Note that this is just a band-aid; a proper fix would declare flink-parent as the parent of force-shading, but this is the easier fix.