Ever driven a car through a field? What looks smooth is often anything but, and airliners are simply not designed to take off from unprepared surfaces.
Flattening frozen ground seems significantly more difficult than just laying down panels.
Ice runways are relatively common in some places. They pump water water onto them to create a flat surface. Similar to ice roads used for accessing oil fields and mines.
I suspect the biggest concern operating off of an earthen runway is ingestion of FOD. For unimproved runways the 737 Classic could be fitted with so-called gravel kits to reduce the chances of ingesting crap from the runway on takeoff. That's why you still see 737-200s in service in the wintery parts of Canada – the fans on the NG and MAX (and A320) are too big to make gravel kits practical.
However, where the weight itself is an issue, Indian Airlines (now Air India) ordered some A320s with beefier landing gear precisely to operate something that heavy off of less than great paved runways.
Ural's not going to have much in the way of manufacturer support though so their options are a bit limited.
Flattening frozen ground seems significantly more difficult than just laying down panels.