Grabbed the 2.1.2 dmg, opened it, dragged, chose Merge (which might have been a bad idea; if it matters, the background image in the DMG ought to be changed to say so), and then I went into a loop:
First time: Launches, no system errors about Gatekeeper as in my earlier posting, dies with no message.
Second time: Launches, gives a dialog box about the temp directory being locked (without saying where it thinks that is, about which I will RFE later), dies with, otherwise, no message.
If I manually remove the lock file in the tempdir, we go back to First time.
I redid the drag-install, wanting to choose replace, but I didn't get the choice. Same results.
So I renamed the folder under Applications to 2.1.0-Audacity and did what I assumed was a clean drag-install from the DMG. Still the same results.
ISTR there's somewhere I can find out why it thinks it's dying, but I cannot recall where that is. Can anyone tip me off?