I most definitely agree that someone looking for a service dog prospect should not be looking at breeds known to be hard, sharp - difficult. I'm sure some of them can be great at it, but training them would not be for a first-timer.You're not going to find a "hungry" reputable breeder, especially if you're after a rarer breed. Most reputable breeders have one litter a year, and they might be spoken for years in advance.
It also seems to me anyone with "debilitating social anxiety" ought to think long and hard about how they're going to train a service dog, which surely needs socializing out the wazoo on their own.
Anyway, the reason I quoted Lillith above is to mention that my experience was that when I changed to looking for a rarer breed, there were more breeders willing to talk to me, and the wait time was a year or less. I started out looking for a Shiba. Honest to Pete, the good breeders have what seems to me to be a 10-year wait list of 100-200 people. Even if they weed that down when the time comes, it's a breed that has small litters, so people who breed only once or a couple of times a year don't produce that many. Consider they want to keep one, they pretty much always have some friend whose going to get ahead of strangers, etc., and you can figure how many are actually available to someone who contacts the breeder out of the blue. They don't even bother being encouraging, just stick you on the wait list as #137.
When I switched to German Pinscher, prospects were much improved. Admittedly the first breeder I talked to had a contract I wouldn't have signed in a million years, but that only means he wanted more control than I was willing to give. He was a good guy with nice dogs and trying to protect his puppies, but IMO he was going a bridge too far.
The second breeder was cooperative, then not. I think I asked too many questions about health clearances, and it seems to be a breed where some breed earlier than 2 based on prelims. Instead of an explanation I got ghosted, which is okay. I don't want to deal with anyone who won't discuss things like that without getting defensive.
The third breeder is the one I got my puppy from. I would have been on a wait list for 6 months or more, but someone who wanted a show prospect backed out on the puppy that is now mine right when I was talking, emailing, and doing a Zoom chat with her. I think that backing out was valid; his back end isn't what I'd want for the breed ring, but I don't want to show in conformation, and I'm happy. This breeder told me she gets about 120 people filling out her online questionnaire for every litter and can weed that down to about 20 just based on their answers there. Then in person chats narrow it further.
At a guess I got offered that puppy over others who may have been waiting because it was right when we were talking, and I'm retired, no kids, have experience with working dogs, etc.
Anyway, I suspect getting a well bred puppy before you're too old to care is easier with rarer and less popular breeds just because there's less demand. It can't just be that the breed is difficult because both Shibas and GPs are considered to be that.