How come I see the outcomes of a 3yo commit only now?
Could the code had been uploaded to debian repo recently?
Could the code had been triggered by other changes?
What if some *other* code changed that (attempts to) read(s) if the bluetooth device is known/authorized, and that code fails to do so. That would explain why the popup would be triggered. Alternatively, maybe Debian recently changed/patched where this bluetooth authorization is saved and the KDE/Plasma codebase doesn't expect that new location.
Maybe the above gives you ideas that help find relevant bug reports or commits.
Best and good luck,
Thom