Manually installed extensions appear as Orphan Extension inside the Extension Manager

Inkscape 1.4.3 (and 1.4.x built from source) on Windows 11.

I have installed Simple Python Scripting by extracting the zip file to my user's extensions folder.

The extension runs fine, but inside the Extension Manager it appears as "Orphan Extension". This happens also with a couple other manually installed extensions that I tested.

When I click the "Details" button nothing happens, but when I close the Manager window I get the following exception:

Traceback (most recent call last):
  File "D:\dev\inkscape\inkscape\build\inkscape\share\inkscape\extensions\inkman\inkman\inkman\gui\main.py", line 238, in local_information
    self.load_window(
  File "D:\dev\inkscape\inkscape\build\inkscape\share\inkscape\extensions\inkex\gui\window.py", line 108, in load_window
    return self.gapp.load_window(name, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\dev\inkscape\inkscape\build\inkscape\share\inkscape\extensions\inkex\gui\app.py", line 136, in load_window
    window.init(*args, **kwargs)
  File "D:\dev\inkscape\inkscape\build\inkscape\share\inkscape\extensions\inkex\gui\window.py", line 102, in init
    self.load_widgets(**self.args)
  File "D:\dev\inkscape\inkscape\build\inkscape\share\inkscape\extensions\inkman\inkman\inkman\gui\info.py", line 106, in load_widgets
    self.inx.add(item.get_inx_files())
                 ^^^^^^^^^^^^^^^^^^^^
  File "D:\dev\inkscape\inkscape\build\inkscape\share\inkscape\extensions\inkman\inkman\inkman\package.py", line 183, in get_inx_files
    PackageInxFile(self.remote(f"../{name}").normpath())
                   ^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: 'NoneType' object is not callable