> After the 2019 closure of the Puttgarden-Rødby service between Germany and Denmark and the seasonal Sassnitz-Trelleborg route linking Germany and Sweden in 2020, the Intercity is now the last one running. All the rest were replaced by bridges or tunnels, or proved too expensive to maintain as demand fell in favour of air travel.
The route actually does still run, of course, but it takes the long way around via land until the Fehmarn Belt tunnel[1] opens around 2029.
BTW. I was on the Hamburg-Copenhagen train on the Puttgarten-Rødby ferry in 2015 during the height of the Syrian refugee crisis. I had changed my booking to earlier trains because of expected delays. It and connecting trains were packed, as were the train stations, also with immigration officials and volunteers. Brings tears to my eyes to this day.