Same issue. Experimented with CFBundleDocumentTypes, UTExportedTypeDeclarations, UTImportedTypeDeclarations, UIFileSharingEnabled, LSSupportsOpeningDocumentsInPlace with no success. Seems to be a bug in iOS 17, and it still persists in Beta 17.1 (21B5045h).

I wonder if this restriction applied only to Airdropped files, or to any custom file types? I noticed that my app's custom file type wouldn't open in the app automatically by the click on it in Files app even if I moved that file to the Files app manually, not via Airdrop. Though other file types (eq. .epub, .fb2) continue to open in their corresponding apps. Do I need to provide some additional setup to custom file type? Now I have the same custom type registered in both DocumentTypes and Exported Type Identifiers on my target's Info tab, and it opened in the app before iOS 17.