There are tax exemptions but during corona Skatteverket has stated that most of those cases aren't eligible for 2020 [0] (answer to the question "Kan jag göra några avdrag med anledning av corona?"):
> Du som under 2020 har jobbat hemma med anledning av pandemin kan som regel inte få avdrag för exempelvis arbetsrum, bredband, möbler eller kaffe, även om du har haft de kostnaderna för att du har jobbat hemma.
Translating:
> Can I make deductions due to corona?
> If you have worked from home in 2020 due to the pandemic, you cannot normally receive a deduction for, for example, workplaces, broadband internet, furniture or coffee, even if you absorbed the costs by working from home.
There are some requirements, you can't use the room for anything except work, it must have a lockable door, etc;
There's some consideration too for broadband, though I don't speak Swedish well enough to be able to file this for myself.