When it comes to extensive studies on stray dog behaviour and niche, from my experience Russian studies are one of the best if only because they use large enough sample sizes to draw conclusions and observations from. In fact, I could remember that there were several types of dog niches and behaviours.
These include owned dogs in outside enclosures (which is really how most owned dogs are), wandering owned dogs, beggar dogs, scavenging dogs, proper indoor dogs and truly feral dogs. Maybe not exactly but that’s what I recall getting from Russian websites. At least with the help of Google Translate for those who are really curious about it.
Andrei Poyarkov’s studies on dogs is a great starting point because it’s so extensive and influential that you have others expanding on his observations. It’s a good enough that they have come close to studying every niche dogs occupy.