Observe https://github.com/jenkinsci/template-project-plugin/blob/master/src/main/java/hudson/plugins/templateproject/ProxySCM.java#L50

The function it's overriding is now deprecated: https://github.com/jenkinsci/jenkins/blob/fd42e33d619597ee4f3e7648792f4541ad6cc089/core/src/main/java/hudson/scm/SCM.java#L483

This throws errors when used with multi-scm plugin ... but fix is in template-project plugin.