There’s a very comfortable overnight ferry from Oslo to Copenhagen, from where the boat train (it splits into multi carriage sections on a rail ferry to cross the femer belt) can get you to Lubeck, Hamburg and then onwards to Amsterdam and Eurostar.
Night 1 on the ferry, night 2 say in Hamburg, final night in Ams or Rdam or Ghent or whichever Benelux city connects you to Eurostar.
Recommend (as others have above) to research rail on Seat 61, get yr rail tkts at Trainline, and find yr ferry tkts at Direct Ferries.
Did the Coph/Oslo ferry trip a number of times in the course of business travel, and rail Coph back to Hmbg as well.
Let’s know how you get on, it’s an interesting and comfortable trip.
DFDS run the Olso/Coph service dep 1500h arr 0900, at least current summer sched. Stena Line run the Gothenberg/Keil service but that’s a few more connections/distance.