New user - creating an appimage from a 'foreign' .deb file

I have a set of printer/scanner utilities that I want to make into an Appimage because they won’t install successfully on Ubuntu systems newer than 20.04, even on Ubuntu 20.04 I need to install some old gtk2 support files from a non-Ubuntu PPA.

The main reason for not installing on newer systems is dropping support for Python 2 and the many and varied changes in Python relating to GTK GUI support.

The utilities are in a .deb file which I have downloaded. I can follow the part of the ‘how to build an Appimage’ which relates to a local .deb file. That seems OK, but the .deb installs
several Python 2 executables and some .so libraries and I’m not quite clear how the Appimage format supports multiple executables.

Also I want the Appimage to have Python 2 in it as it will have to run on systems without Python2.

Any pointers to help, examples, sections of the documentation to help me on my way would be very welcome.