I lied about it being the only winter boot I've ever owned.
Dunlop ice bears. Hands down the BEST csa approved work boot. Fully steel free, rated to minus -50°C, again vapor barrier socks are key, or you can also put plastic bags directly against your feet, then wool socks over top in a pinch. Last winter I was working 60 feet in the air on a aerial work platform(that's a whole different issue, hydraulics don't like to work too well) and it happened to be the coldest place on earth for that particular day coming in at -53°C
right after I got off, the linesman were working on the lift and it froze up solid, stayed like this for about a week until the weather warmed up and we had heaters plowing on the solenoid valves and hydraulic tank
Ice fishing on one if said days near -50 with wind chill, it was only about minus 40 but quite windy that day. Caribou gloves, beaver lined and goose down parka on top of base layers