How to track field changes in custom (ECK) entities I'm using Feeds to import an online spreadsheet into Drupal (ECK) entities.
This goes okay but there doesn't seem to be a module (?) that allows to view the tracked changes in the entity fields.
There is one module that is promising but doesn't yet support custom entities: "Track Field Changes"https://www.drupal.org/project/track_field_changes

So the question is: is there an alternative module or way to view changes of entities, especially the field changes?

I tried the diff module but that doesn't give an overview of entities that have changed?
You can try ECK Revision module. Also check related drupal.org issue: Support Revisions in ECK.