Thanks - if I were seriously in need of DT I’d go this route. Or perhaps even wipe my system clean and start scratch with a fresh Linux install. Darktable used to function on this machine. Now it doesn’t.
But I’m not in need of the app at this time. If there were a simpler fix I’d gladly pursue it. Apparently not.
For now I’ll chalk up darktable as one of those apps that doesn’t want to behave properly on my platform. Thank goodness there are other outstanding options.
If I ever tumble across a fix I’ll share it here for posterity. 