It’s even worse than I thought. It appears that Adobe deliberately caused the “Lightroom [etc] will not start” issue!
This apparently from Adobe:
So Adobe installer screws up the folder owner/rights; then Adobe causes their apps to refuse to start when it detects the issue. And they give no information: the fix (below) is out there, but you have to Google to find it.
Absurd that Adobe can do this: stop people’s business cold, deliberately. A bug is inevitable and forgivable, but a deliberate decision to not allow the app to start when they detect it, is unforgivable.
Almost enough to give mega-corporations a bad name.