My parents watched my sister's dog while she was away, it barked constantly when it wasn't being entertained. To the point the neighbours asked if it was my parents' dog and that it was bothering them, I felt so bad even though I knew the date the dog was leaving. I don't understand how people can just just let their dog bark and bother everyone else (let alone not care the dog is obviously not happy).
Seems to me there's a root cause of why the dogs are barking that should be addressed. Are they hungry? Thirsty? Anxious? Bored? The neighbour should be figuring out what the root cause is and addressing it. Dogs usually bother more than just the immediate neighbours, maybe coming to them with signatures from more neighbours in combination with a solution (help in that clicker training, or maybe they can get some help with training
https://www.barkbusters.ca/calgary-dog-training/) will result in a bigger effort to fix it.