The whole question is in the title: the choice of user lists disappeared with the 5.10.12 release.
I can't reproduce your issue. Can you be ore specific about the issue? Don't you see any lists at all? Or is not possible to select a list when creating a newsletter? Front-end? Back-end?
See attached captures.
Capture B corresponds to the last newsletter at the top of Capture A.
In the second image in the righthand column the tab "Attachments" is active. You should see your lists when you click on the tab "Lists".
Ok, thank you
You're welcome, enjoy your Acymailing!