Dear Imants,

Is it possible that some ghc version is installed with /usr prefix, and another with /usr/local ?

If yes - try uninstalling the older versions. You may need to clean up the obsolete library folders.

Joy! Which is to say, after several unsuccessful attempts involving progressively more draconian deletion strategies, ending with % uninstall-hs all --remove and reinstalling the Core Platform from the installer, which finally worked. Many thanks! Peace, Stu