The Loyal Hound was a life saver for us. We are based in Boston and dropped off Nacho (3.5 yr large mutt) at their New Hampshire location. The trainer who worked with Nacho was Jay. For years we've been having trouble with aggressive reactivity, especially in the house. We first got Nacho at 4.5 months old (past his socialization period) and he had almost zero experience with humans. He had been in at least 3 shelters that we knew of before we got him, so we knew he was going to be a tough dog.
He was OK at first, was good with visitors in the house, but as he started adolescence his aversion to people got worse and worse. We couldn't have people over without leashing him (and, eventually, muzzle training him). We went to the MSPCA for training classes, worked with a couple different trainers one-on-one, gave him plenty of exercise to tire him out, tried natural calming treats to help with anxiety, and nothing worked long term. And then during quarantine, it completely got out of our hands.

Since no one could visit, all of the exposure training we had worked so hard with him on for so long, faded (as it does when skills aren't being used). New visitors coming into the house didn't feel safe with him in the same room, even with a leash and a muzzle. He snarled, barked, postured, and even attempted to bite them (and thankfully couldn't because of the muzzle).
My partner and I finally came to the conclusion that we needed to do something more dramatic, we had done all we could on our own. We did a ton of research and finally decided to contact The Loyal Hound and it was worth every single penny. Everything they did was about the dog, not the money. Scheduling was tough to start and it was a little frustrating - we weren't sure what day we could drop him off until almost the week of. And we knew it was because they had to wait for another dog to be ready to graduate, which is awesome, so we managed with our tough work schedules to make it work. We were anxious about introducing Nacho initially since we hadn't met Jay in person yet (pandemic), but he was really good with him. He didn't act aggressively to establish dominance, he didn't force any touch, he just let Nacho roam around the training room, sniff, and explore. With some treats and time, Nacho was comfortable and we felt OK leaving.
The first week Jay and Nacho just played. Lots of treats, outside time, toys. The second week they actually started the work after Nacho was able to settle in and bond with the trainers. They worked on training him on a long lead for about a week and a half (a few days longer than planned) and then moved onto completely off leash training. They were able to take Nacho in public, through stores, introduce new people. The communication was fine, they were definitely busy but I could tell Jay was making an effort. We had a handful of phone calls and daily/every other day texts - Nacho was doing well, he was eating, playing, responding well to training, no incidents. No news was good news. When we went to pick him up, Nacho was definitely thinner (thinner but fitter, he was a little chunky before because he likes to steal food from the kitchen counter), but he was clean and happy. He was super excited to see us. Jay let us say hello, get some of that energy out, and then we started our training session (just as important, if not more important, than Nacho's training). He was patient but strict and we were able to get all the major commands down in an hour. He sent us home with Nacho for a couple weeks to practice, and then we had a follow up appointment so we could refine what we learned.
Nacho was definitely a little weird the first couple days home - he was re-adjusting. But he was back to his normal self within a few days, but way less anxious. Jay trained him on an e-collar, which we were really unsure about going into the training - there are so many horror stories. But their mentality is that the collar should never be used as a punishment - it should be used to get the dog's attention IF they aren't paying attention or are ignoring you when you try to get their attention verbally. The collar they gave us has about 100 levels - we have Nacho regularly on a 5-6. I can't even feel it until 10-15 and it's static electricity, not a zap, so it doesn't hurt, it's just uncomfortable. And, most importantly, the e-collar changed Nacho's quality of life. He still gets anxious without it, but as soon as we bring the collar out, his tail is wagging and he gets wiggly, sometimes so much so that it's hard to buckle the collar. And his anxiety just melts away because he knows if we need something from him or he's doing something wrong or dangerous, there's an easy way for us to get his attention and let him know.