If it is a desktop-type application, just use CPython itself? It has good embedding support since forever, and is the "Python" that most people know and are used to. Best compatibility with existing code, for third party libraries and tooling. https://docs.python.org/3/extending/embedding.html

Many applications in the graphics space embed or otherwise allow Python scripting. Some open source examples are: Blender, FreeCAD, GIMP, Inkscape.