Is there a way to list all items (maps, apps, dashboards etc.) that are consuming a specific web layer within our enterprise portal?
Take a look at the technical article linked below. It walks through how to list all dependencies using the ArcGIS API for Python's dependent_upon() and dependent_to() functions. Some tweaking will be required to get it to list specific layers, but hopefully this is a good place to start.
How To: Find dependencies in Portal for ArcGIS using ArcGIS API for Python
Louis K. I was working on a tool you can try that may give you the functionality you need:
Report ArcGIS Enterprise Item Dependencies
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