Q: Where are Email-to-Case Attachments Stored? Attachments to an email-to-case email are displayed as Files but are not stored as Files or as Attachments. Can anyone tell me in which object those attachments are stored?

A: Assuming you have Email-to-Case Settings Save Email-to-Case attachments as Salesforce Files checked true.
Files are saved as:

*

*ContentVersion

*ContentDocument (parent of ContentVersion)

and linked to the EmailMessage child of the Case using a

*

*ContentDocumentLink
You can see the Schema here in the Salesforce Object Ref
