DIRTY_PAGE_POLL without activated Indirect Checkpoint
According to SQLSERVER-DBA.COM

The background-thread is waiting to poll dirty pages even when indirect checkpoints are disabled (which is the default setting of each database)


  The interesting aspect of DIRTY_PAGE_POLL wait type , is it still appears as a wait type, even though Indirect Checkpoint is not enabled, as the background thread  is waiting to poll for dirty pages.