This problem is trivially fixed with blackout curtains. Dealing with lack of sun is harder.
Blackout curtains don't form a good seal and always let light bleed through around the edges.
As someone who lives in Sweden, I can’t agree there.
Lights can never fully replace sunlight. It’s not even close.
I've lived in Sweden my whole life, and in Norrbotten for a decade.
And if your blackout curtains don't work, get better ones. Many Nordic households have double curtains, one solid plastic to block the vast majority of the light and the other from cloth to diffuse/block the rest and look pretty.