Hienas were often kept as pets in acient times
it was a kind of luxury pet for animal traders and rich decadents
the observation about breeds of domestic hienas that could be ridden isnt so inprobbable
theyr stamina does in fact not suck, they can endure a lot and keep on going withouth food or water much longer than dogs, or even most wolves
their whole sceleton is built for long marches
also hienas, when fully grown, are much stronger than dogs, especially in the jaw muscles and legs
the problem would be their mentality and behaviour
hienas are regarded by manny cultures as vile and detestable creatures not just becouse they eat carcases, they are cunning, agressive, greedy, dominant creatures
even with domesticated dogs there are breeds and individuals you can live with like friend and family, and that act ok with other dogs, and breeds that will make your life a living hell if you show the slightes weakness or lack of controll and have the habbit of eating other peoples pets if not on a leash and musle, althou with dogs much depends on upbringing, training and proper socialisation
with hienas just multiply that with 10
people training hienas would probbably be trained themselves in specifically training hienas and this would probbably be a family buisness
one interesting cultural influence might come from hienas having dominant females, wich have false penises growing in the abdomen-groin area, wich they sometimes ewen use, in certain situations
the domestication of these creatures would probbably influence the perception of gender roles and stereotiping, even if olnly by pointing out "the wrong way"
in most breeds, large numbers of females would probbably be sterilised as soon as possible, as they grow really big and get really agressive