So here’s what I found on SAS website
To confirm my suspicion that there’s something really weird going on, I did a trial search
EWR-OSL for June 28, 2024
ARN-EWR for July 13, 2024
Note, these were the dates that IND-OSL/ARN-IND showed NO flights whatsoever on the same website.
The search from EWR for the exact same dates resulted in tons of flights in all fare classes. And I know that there are a plenty of United flights between IND and EWR on these days. Based on this, I’m convinced that all segments of the desired itinerary are available, but none of the websites (SAS, United, Air Canada, Google Flights, even ITA Matrix) could show this itinerary. So, there’s something really weird going on, and I need to find out how to get around it.