It’s not modular, but Hexayurts are popular at Burning Man. They are just alumium skinned foam panels held together with fiberglass reinforced tape. Quite sturdy, and very warm.
I see that a 20’ shipping container weighs 5000 pounds and a huge ATV can tow 1100 pounds. Cut that shipping container into 6. slices, weld flanges on them, add your doors and windows and shit. Haul your house out in 6 trips. Bolt it together in place.
Polyurethane foam - you can get it as a two-part kit that starts expanding the moment you mix it - very compact to carry, but very high volume once mixed - and it’s a great insulator. It can be injected into sealed plastic bags and these placed inside a box - and when it expands and cures, the bag with the set solid foam block will just pull out.
You might need to manufacture the foam units inside some kind of heated shelter though, as the foaming is a chemical reaction that probably doesn’t work well in the cold.
On their own, they’d not be a brilliant building material, but they could be fixed together by skewering them onto vertically-set rods to make a wall, which could then be faced with thin plywood or something
Does this structure need to be bear-proof?