A lot of the extensions don't work out of the box. The logs complain that it can't find python in the path.

Script::resolveInterpreterExecutable(): failed to locate script interpreter 'python'; 'python' not found on PATH
virtual bool Inkscape::Extension::Implementation::Script::load(Inkscape::Extension::Extension*): assertion 'command.size() > 0' failed

So I did this

  <group
       id="extensions"
       python-interpreter="/usr/bin/python3"
          />

Now my extension loads, I can see the panel. But it errors out

Python path configuration:
  PYTHONHOME = '/tmp/.mount_InkscagAivoj/usr/'
  PYTHONPATH = '/home/username/.config/inkscape/extensions:/tmp/.mount_InkscagAivoj/usr/lib/share/../../share/inkscape/extensions:/tmp/.mount_InkscagAivoj/usr/lib/share/../../share/inkscape/extensions/inkex/deprecated-simple'
  program name = '/usr/bin/python3'
  isolated = 0
  environment = 1
  user site = 1
  import site = 1
  sys._base_executable = '/usr/bin/python3'
  sys.base_prefix = '/tmp/.mount_InkscagAivoj/usr'
  sys.base_exec_prefix = '/tmp/.mount_InkscagAivoj/usr'
  sys.executable = '/usr/bin/python3'
  sys.prefix = '/tmp/.mount_InkscagAivoj/usr'
  sys.exec_prefix = '/tmp/.mount_InkscagAivoj/usr'
  sys.path = [
    '/home/mwinoto/.config/inkscape/extensions',
    '/tmp/.mount_InkscagAivoj/usr/lib/share/../../share/inkscape/extensions',
    '/tmp/.mount_InkscagAivoj/usr/lib/share/../../share/inkscape/extensions/inkex/deprecated-simple',
    '/tmp/.mount_InkscagAivoj/usr/lib/python38.zip',
    '/tmp/.mount_InkscagAivoj/usr/lib/python3.8',
    '/tmp/.mount_InkscagAivoj/usr/lib/python3.8/lib-dynload',
  ]
Fatal Python error: init_fs_encoding: failed to get the Python codec of the filesystem encoding
Python runtime state: core initialized
ModuleNotFoundError: No module named 'encodings'

Current thread 0x00007f3b4c881740 (most recent call first):
<no Python frame>

I am updating an extension to work with Inkscape 1.0. I was working on a MacOS machine before, and my extension was able to run.

Does this work now with the released version?

Got bit by the above failure and error output too running Fedora 32 Linux when using the latest AppImage variant:

https://media.inkscape.org/dl/resources/file/Inkscape-4035a4f-x86_64.AppImage

On Flatpak ~/.config/inkscape/extensions weren't found at all.

On Snap variant extensions worked just fine.