We can mutate it. Before having seen your work, I similarly had sunk a few hours into trying to re-locate that 'local_unit' data, then researching sites that would provide me other official lists of administrative areas (i.e. direct from gov; trying to avoid wikipedia and third parties). I didn't get too far; seems these information are generally absent and that which did exist are slowly disappearing. My intention was to somewhat document this... preserving original sources, then building it out ourselves.
Please just try, if possible, to also keep the simplification occurring within the notebook. I should have similarly stepped through the transformation of shapefiles into geojson.