"/keybase/Portable Keys is not a Keybase folder"

I don't know where this warning keeps coming from, but it pops up several times per day. I also realize it might not be a keybase issue per se, but I don't know where else to ask about it.

Clicking on it does nothing and shows me no additional details. My best guess is that I have another application or service running that tries to read or write a `Portable Keys` folder, but I don't see it affecting any other mounted volumes. Google also comes up with nothing useful or informative.

Any suggestions on how to track down the culprit would be greatly appreciated.

Start by reproducing the warning and inspecting the notification shown in the attached screenshot; no source file, test, or entry point is named. Trace which Keybase component or other application accesses “/keybase/Portable Keys,” then document the culprit and a way to prevent or resolve the repeated warning.

Written by the indexing model from the issue text.