I recently learned about the Priority 600 - https://www.prioritybicycles.com/products/the600 - and have been very taken by it. It has 12 speeds, not 20, but the Priority gearbox's 12 speeds have no overlap. The tires look as though they would provide good shock absorption. And the gearbox seems less prone to damage and wear than a derailleur.

Of course, tastes vary, but I thought you might consider this for your trip back. :)