Have you tried carrots? They can grow in negative 8 degrees Celsius (around 19 degrees freedom units)
I think broccoli and Brussels sprouts also do well.
When it comes to cucumbers, however, growing a ton, and pickling them is perfect for using all year round, and pickling is also way easier than I first thought.
I’ve never tried this but how about one of those small DIY greenhouses? Apparently they’re pretty easy to make. I’m not sure how cold it gets at your latitude but with a greenhouse you could manage to lower your zone a level. Maybe enough for those carrots.
Worst case I guess is just grow winter crops during the summer. Half a year of cheaper food is better than nothing.