Donkey
Bred in desert country, so it thinks before it moves, which reads as stubbornness and is really caution. It remembers ground and company for decades.
Overview
A donkey is not a small horse, and treating one like a horse is how they get ill. They evolved on poor dry ground, so rich pasture gives them laminitis and excess weight, and their diet is properly built on straw and low sugar hay rather than on grass and hard feed.
The second difference is more serious. A donkey that stops eating, for any reason, is at risk of hyperlipaemia, where fat floods the bloodstream faster than the liver can handle. It is life threatening and it is triggered by stress and pain as much as by diet. A donkey off its food is an emergency, not something to watch overnight.
Temperament
Careful rather than stubborn. A donkey that refuses to move is usually assessing something it does not trust, and pushing it harder confirms the fear. They learn quickly from people who are patient and remember people who are not.
They bond hard, usually to one other donkey, and separation from a bonded companion is described as the most common and most serious cause of stress in the species. That is not sentimentality: the stress of separation is itself a trigger for hyperlipaemia. Keep them in pairs, and if one has to go to a vet, the companion goes too.
Care and grooming
Barley straw and low sugar hay as the base, with grazing restricted rather than unlimited, and a body condition check by hand every few weeks.
Hooves need trimming every six to ten weeks and donkey feet are shaped differently from a horse's, so the farrier needs to know donkeys. Their coats are not waterproof the way a horse's is, which is why dry shelter they can use whenever they like is a requirement rather than a nicety.
Living and exercise
Half an acre each is workable, with the emphasis on dry standing, shelter and a track to walk rather than lush grazing.
They live 25 to 40 years, which is longer than most horses and long enough that rehoming plans matter. Give them things to do: donkeys are intelligent, they get bored, and a bored donkey chews fencing, trees and anything else within reach.
Something here wrong or out of date?