Yup. This goes for ANY type dog. And if the dog isn’t properly trained to the fence, when the adrenalin rises, many dogs will ignore the underground invisible fence.
To simplify things let’s identify the problems here:
An unfenced yard is not a safe environment for a big dog. Most rescues, breeders have already told her this, by refusing to adopt to her. Hint: Fence your yard.
OP wants a big tough intimidating dog, but is unable or unwilling to control or train it to comply.
OP does not want to spend $$ to hire a trainer to help with training.
OP is not interested in a milder temperament dog who is probably easier to train and contain.
OP has physical limitations which prohibits adequately exercising dog and providing enrichment.
OP does not want to spend money or time to purchase a more appropriate puppy and train it to be a good family member.
OP refuses to acknowledge there comes a time because of age or disabilities that the dog we
were OK with at a younger age, is totally inappropriate as we age.
OP must change her thinking and accept those things that we cannot change.
If I were a breeder or rescue I would never adopt a dog to OP without a safe yard and willingness to seek out proper training for the dog when it needs it. This is a recipe for disaster.