Swish is great, but it is sensitive infrastructure. It has already been down multiple times due to DDoS attacks (together with BankId). Don't let Swish completely replace a stash of cash at home.
There are lots of places where most customers still pay in cash. Mostly ethnic minorities in stores that cater for ethnic minorities. I find it interesting that ethnicity or religion would end up being a signal informing if one is using cash or digital money.
Curious where abouts you are in Sweden? (i.e. how far north/south).
I'm not Swedish but a lot of my family are, so I visit fairly often. In Gothenburg at least, it's pretty standard in my experience that small grocery stores won't accept cash. I won't pretend that generalises anywhere else.
Many many restaurants and stores never accept cash here. This would be a huge problem if cash suddenly becomes the only way of paying for everyone at the same time.
(tldr Sweden is pretty cashless and a lot of shops don't accept cash)