Bergen to Oslo Rail Trip

https://community.ricksteves.com/travel-forum/norway/nin-what-side-of-train-bus-has-best-view-of-scenery

From Bergen to Oslo my preference would be to sit on the right-hand side of the train. Throughout the ride there are good views from either side but, to me, the most spectacular part of the trip is up in the mountains with all of the lakes and snow. Most of this is best viewed from the right as many of the views to to other side are up against steep hillsides.
Coming out of Bergen there are some fjord views to the left hand side of the train.
Once you are out of the mountains going towards Oslo there is just forest and a few towns that aren't particularly picturesque...it really doesn't matter where you sit.

While I agree that the right side viewing the Hardangervidda is the more scenic side, keep in mind that it is a train and you don't have seat belts and attendants demanding that you stay in your seat.

Remember that about half the seats face backwards, which for many people is more important than which side of the train. Also, the train trip is beautiful, but not any prettier than driving up to Whistler in Canada or crossing the Cascades in Washington.

Wilma

You can see what the trip is like on Netflix. They are playing an unedited filming of the entire trip. I have watched about half so far. The beginning of the trip is better on the left, then later better on the right. As mentioned above move back and forth if able.