Joplin 2.5.1 (prod, win32)
Client ID: 67a5658fc1484adf927f4bd6f8e8a8dd
Sync Version: 3
Profile Version: 39
Keychain Supported: No
Revision: b6b972b
Win10 Pro x64 21H1
@markrenier it does not appear to be your setup or flash drive.
I just tried to update a plugin (using 2.5.1) to see if I could duplicate the error and I can.
Apparently EISDIR means:
... that the target of the operation is a directory in reality but that the expected filetype of the target is something other than a directory.
Also I notice that the second path shown does not look like a valid path for Windows (forward slashes)
EDIT:
Could not install plugin Error EISDIR illegal operation on a directory
Just adding these keywords as so far the error has only been posted as an image. If anyone searches for this error this post should now show up. (Whether they bother to search the forum is another matter!!)