When migrating content with the Drupal 8 migrate module, the creation and updating of new entities may fire lots of custom module hooks. This may or may not be desired; if you have found yourself here, it probably interferes with the source data in a problematic way, or unnecessarily slows down the migration process.
The cleanest way I found to stop specific hooks for specific migrations, is to add a dummy/meta field to the migration and check for its value in the hook.
Include a dummy field in the migration
In the process section of the migration, add a field with a name that will not interfere with any field name of the target entity: