I've posted this on the Arch Linux forum, but there wasn't anything specifically helpful received.

I recently upgraded Amarok from the Arch versions 2.9.0-2 -> 2.9.0.git20180816-1. The major difference in the Arch package is that it upgraded to KF5. To transfer my playlists and preferences, I had to manually copy ~/.kde4/share/apps/amarok to ~/.local/share/amarok, and ~/.kde4/share/config/amarokrc to ~/.config/amarokrc. However, my song statistics are still missing. My understanding is that they should have been stored in ~/.kde4/share/apps/amarok, which I transferred as above, but they didn't seem to transfer okay.

How can I transfer my song statistics from the previous Arch version of Amarok to the current version?

Sadly, you upgrade to a non-released version of Amarok, actually even pre-alpha, so there are indeed hickups to expect.

I suggest you check with your distribution on why they seriously suggest unreleased software to be "upgraded" to. This is completely out of our responsibility.

Thank you for the response. I'll open a bug report for Arch.

And… the response was to drop Amarok from the repos