My dog barks non-stop when I'm at work, neighbours complaining, what to do?

Rescue dogs often bark from anxiety of being left alone, mine did the same, and it got much better with work. What helped: a long walk and play in the morning to burn energy, leaving him a treat-dispensing toy and something with my scent, and slowly training him to be alone (leave for 5 minutes, then longer, rewarding calm). A midday dog-walker or a neighbour/friend popping in can break the long alone stretch if you can arrange it. Some people use a pet camera to check and even talk to them. Please don't consider giving him up first, this is very trainable. If it's intense, get a professional trainer or ask your vet, sometimes there's an underlying cause. And keep your neighbours updated so they see you're handling it responsibly.

From my experience, barking when alone is usually separation anxiety or boredom, both fixable without rehoming, so don't panic. First, tire him out before work: a proper morning walk and play so he's calmer and sleeps. Leave enrichment, a Kong stuffed with treats, chew toys, or a snuffle mat to keep him busy. Practice gradual alone-time training, leaving for short periods and building up, so he learns you always come back. Background noise like a radio can help. If it's severe anxiety, a vet or a certified dog trainer/behaviourist can help, and rule out any health issue. It takes weeks of consistency, not overnight. Also keep talking to your neighbours so they know you're actively working on it, goodwill goes a long way here.