We sailed on the Viking Rinda for the Danube Waltz cruise on April 3, 2022. The cruise was only disappointing in that we wasted $1800 getting a balcony cabin which we found out was NOT worth the expense.
First of all, the balcony's are very small - 3' by 5' - barely enough room to sit in a proper chair. Secondly, and most important to us, the riverboats tied up to each other in the ports at Vienna, Linz, Krems and Batislava and BudaPest, so when you open the curtain to look at the country side in these ports, you are looking into the cabin of the boat next to yours, making the balcony useless.
There are many observation areas in the ship, so save the thousands and skip getting the balcony cabin. Or, spend the money on the other cruise lines that pay for dock space at the ports so you are not looking into the bathroom of the cabin next to yours.
We knew it would be small, but it was smaller than expected. The balcony was useless as it was very small also and in port, the ship tied up to other ships so the view from your room is of the cabin in the ship tied up to yours.
If you can swing it, pay the money saved by not booking a balcony cabin and get an upgraded, larger cabin.