I have a super sparpreis ticket for Nuremberg to Stuttgart on 6th December. The timetable has changed and now this journey is no longer available, and I can select an alternative. The original ticket purchased was for a direct ICE train, and now the only direct option is an RE train. I have also purchased a D-Ticket for my trip. If I hadn't booked this ICE ticket I wouldn't have had to pay out of pocket for the RE trip as it would be included with the D-Ticket. So now if I select the alternative direct RE train I'm basically losing money. My question is, even though it's a super sparpreis ticket, am I eligible for a refund because of the timetable change? Thanks :-)
Yes, if they change the schedule you can request a refund.
You'll need to fill out this form:
https://cms.static-bahn.de/wmedia/redaktion/aushaenge/fahrgastrechte/Fahrgastrechte-Formular-English.pdf
And tick "I did not start my journey..."
(Don't tell them you plan on taking a different train using your D-Ticket. That is none of their business...)
You could also just go to a ticket counter, which might be easier.
Agree to first answer that it is not necessary to tell the long story. Keep it as simple as it is: connection is cancelled, so you want a refund.
Ok thank you so much. 
It's disappointing that there are no ICE trains for that route anymore (except one at ~5pm), especially on a Saturday during Christmas Markets as you aren't guaranteed a seat on the RE trains! Will have to line up extra early.
You do not line up for trains. You just go to the platform, and when the train pulls in just board through one of the doors. Being there earlier than the train does not increase your chance for a seat. But I would not be to worried. At each stop people get off, and seats free up. Those already on the train have first dibs :-)
But probably you will not have an issue getting a seat.
My suspicion is that the line has a reduced schedule because of engineering works. Works they perform at a winter weekend, because demand is lower. That there are Christmas markets on does not change that. People from Nurnberg don't go to Christmas markets in Stuttgart. :-)
One more question actually please. I see now that I can submit the compensation request on the DB app, but it says it can only be done "if the travel period is in the past". Does it make a difference if I do it at a ticket counter, would they accept it beforehand?
That makes sense then for all the ICE trains to be removed, thanks for the info.
I've read some horror stories about regional trains being packed and people having to stand for hours long journeys, especially on weekends, so it's great to hear that might not be the case!
The direct RE trains from Nuremberg to Stuttgart all originate at Nuremberg Hbf. Thus if you get there when they spot the train on the platform,, you will be the first on board to get a seat. So arriving a bit early will pay off. How early? 15 minutes should do it.
I've read some horror stories about regional trains being packed and people having to stand for hours long journeys, especially on weekends, so it's great to hear that might not be the case!
Your train originates in Nuremberg. It is usually sitting in the station 10-15 minutes before departure. If you are on the platform at this time, you will have no problem finding a seat. I would go to the front of the train (i.e., westward). Most people are too lazy to walk those few steps, so there are always seats available in the first cars.
And even if, execeptionally, the train is completely full, that only will be as far as Ansbach (30 min). After that, it travels through the Franconian-Swabian no man's land, where no one wants to go. And it only gets full again shortly before Stuttgart, but that doesn't matter to you because you will have your seat.
Wonderful, thanks everyone!
In the case of a cancellation you should be able to get a refund beforehand as well. The form is not very user friendly, which is why I suggest you go to a ticket office.