1.0.x appimage extensions not working

Steps to reproduce:

• open Inkscape
• draw a path
• try to apply an extension

What happened?

• nothing

from the terminal:

** (org.inkscape.Inkscape:16779): CRITICAL **: 11:00:21.295: Script::resolveInterpreterExecutable(): failed to locate script interpreter 'python'; 'python' not found on PATH

** (org.inkscape.Inkscape:16779): CRITICAL **: 11:00:21.296: virtual bool Inkscape::Extension::Implementation::Script::load(Inkscape::Extension::Extension*): assertion 'command.size() > 0' failed

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After testing in latest 1.0.x, a dialog will pop up, but error message changes to this

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'

Inkscape Version and Operating System:

• Inkscape Version: Appimage 1.0rc1 (09960d6f, 2020-04-09) for initial issue, 1.0rc1 (ad474803, 2020-04-12) displays the later problem.
• Operating System: Debian testing
• Operating System version: Gnome 3.34.2