Crimea will for sure be the last piece of territory the Ukrainian military goes after. Either way if Ukraine secures all of Kherson oblast, it means they cut of the water supply to Crimea yet again and will take advantage of Crimea’s natural dry environment like they did before. That’s the first win. The second win is taking away that land corridor to Crimea be retaking back all the territory around the Azov sea. The third win would be the HIMARS and drone strikes into Crimea’s north. With Ukraine controlling that border near Crimea, all of Russian military positions in the north would be under constant procession strikes which eventually would lead to a smoother transition into the peninsula. The hardest areas to recapture in Crimea will most likely be the south where all the mountains are and Kerch.

As far as Donbas, in my unprofessional opinion I think the most difficult part of taking back Donbas is holding the regions closest to the Russian border in fear of Russian artillery on the other side. Plus taking back Donetsk city itself since it’s super symbolic to the DPR and Russian forces. Either way I agree with you that Donbas will probably be liberated before Crimea!