Version 2.6 on Android 2.3.6: "No calendars found."

[s-m-e]

I just installed this app from F-Droid, version 2.6, onto a Motorola XT320 running Android 2.3.6 / Gingerbread. The phone contains one local calendar, operated by what appears to be Android's stock calendar app of that era. My objective is to extract the (significant amount of) data from this calendar onto a computer. The phone is not connected to a Google account (and never has been). The calendar has never been synced with any other device or service. The device has not been rooted.

Expected behavior: Launching Calendar Import-Export should allow me to export my local calendar's data.

Actual behavior: When launching Calendar Import-Export, I am immediately confronted with a message stating No calendars found. (followed by some advise on how to create one). I can only confirm with OK. The app exits.

What's happening here? How I can possibly work around this issue?

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I posted a longer question detailing my quest and attempts based on other approaches on StackExchange / Android Enthusiasts.