When clicking on Extensions > Manage Extensions, I receive the error:

Traceback (most recent call last):
  File "extension-manager-bootstrap.py", line 131, in <module>
    run_existing(sys.argv)
  File "C:\Users\MyUserName\AppData\Roaming\inkscape\extensions\org.inkscape.inkman\manage_extensions.py", line 43, in run
    from inkman.gui import ManagerApp
  File "C:\Users\MyUserName\AppData\Roaming\inkscape\extensions\org.inkscape.inkman\inkman\gui\__init__.py", line 21, in <module>
    from gtkme import GtkApp
  File "C:\Users\MyUserName\AppData\Roaming\inkscape\extensions\org.inkscape.inkman\gtkme\__init__.py", line 34, in <module>
    import gi
ModuleNotFoundError: No module named 'gi'

It's the first time I've (tried to) opened the extensions part of the tool, never used before, fresh installation.
I've tried to run pip install gi, but pip doesn't know it.

Seems to be working here under Win 8.1, but not Linux Mint 20.

The extension manager is still a beta-testing feature, so unpredictable behavior can be expected.

That said, I'm sure the developers would appreciate hearing your experience. https://inkscape.org/forums/beyond/how-to-report-bugs-or-request-new-features/