What is the quietest place with some industry? [closed]

This is going to be extremely difficult to answer with certainty since you have not specified a distance from city limit or a minimum size of city.

In Croatia there are a number of cities or areas within a city that are pedestrian only. To me this was a huge eye-opening, particularly noticeable when I arrived in a city which did have traffic (Zagred). It was so much more noisy and smelly than Dubrovnik, Korcula, Split and Zadar. Yet not of those places are that quiet since they are quite dense and busy cities (except Korcula).

It would be better if you were out of city for overall quietness, so choosing a smaller city which allows you to be out of the city while not being far would probably be best. Maybe a small city in Switzerland or Montenegro. Due to the landscape, both these countries have small cities with sparse quiet areas around, instead of the more common enormous metropolitan areas that sprawls into suburbs which is common elsewhere.

Northern Denmark also has relatively isolated towns in the north yet some are big enough to support a good number of tech companies. So if you allow yourself to be 30-45 minutes away from the city, you can find quiet places.

If you are a Software Developer, it's becoming very common to find 100% remote jobs, so you can then choose the location and do not even need to work close to a city.

Therefore, if you decide to work remotely, the choices are just limitless.