[Q] Accessing logs on the debug

This is for: Samsung GT-I9300 (Android 4.1.2 Phone)

Context: We are mobile development consultants and one of a beta versions of the an app we did for client is crashing on client's devices. (It was delivered through Testflightapp but since the app immediately crashes before the testflight session begins, we don't see any debug logs or crash log via testflight)

We want our client to send us the logcat contents so we asked him to:

1) Turn on the Developer Options from Settings/About Phone/ and Touch 7 times on the "Build Number".
2) In Developer Options you will see "Take bug Report". Touch it and Touch Report and it will take some time to prepare the email. When the preparation is complete you will see a notification which will ask you to Share the Report.

He replied:
Looking in developer options and I don't see anything called "take bug report

We then actually checked the user manual of Samsung GT-i9300 Galaxy and it does not have the 'take bug report' feature.

Question: How can we access the logcat contents from the client's device without resorting to integrating a logging framework in the app ?