Hi @Chirannjevi Panala,
I'm afraid there is also no Graph API or PowerShell can fetch all the user's OneDrive files that are being accessed by external users. This OneDrive activity reports can get the activity of every user licensed to use OneDrive by looking at their interaction with files on OneDrive. Unfortunately, external users and activity like accessing file via shared or direct link are not supported. I suggest posting feedback to MS via this feedback portal: https://feedbackportal.microsoft.com/feedback/forum/ebe2edae-97d1-ec11-a7b5-0022481f3c80.
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