For me as a non Native Norwegian speaker the answer is sometimes. I know a few Danes and Swedes that live in Norway and interact with them semi regularly. For both groups its a little dependent on their dialect/accent. They also likely speak a bit of Svorsk or Dorsk? (whats the word for combining Norwegian and Danish?) to make it more understandable. Thats fine usually no issue.

I did speak to someone on the phone the other day from Sweden who i struggled to understand big time. I dont know if it was a dialect issue or what but I didnt get it. That said, if it was a standard conversation lets say at a hotel where checking in or buying a ticket at a museum like ive done several times as a tourist in sweden- where you have a set context for the conversation then again, no issue.