The heating issue maybe resolved with a dealer update to the car, people in the UK are reporting there issue resolved after the dealer had done an update.It seems the EV6 does quite well in winter conditions, at least according to this Norwegian review. Some issues with front window fogging when driving in tunnels and one issue where the heating suddenly turns off. The latter is supposedly fixed when restarting the vehicle. Apparently even the RWD version has really good traction in snow mode and both RWD and AWD versions behave well on winter roads. Consumption was estimated to 338 km for the RWD and 284 km for the AWD. This was estimated in snowy conditions at -4°C when starting from a cold battery and driving a 71 km route with 50 % B road and 50 % highway. He also comments on the lack of a rear window wiper, saying that most of the snow accumulated beneath the window and that the window heater + air circulation mostly kept the rear window decently clear when driving. All in all quite reassuring for winter driving I'd say.
Kia EV6 på vinterføre, vi testet både RWD og AWD (des 2021) - Nybiltester