Hello all. We’re scheduled to arrive in Frankfurt via Iceland on Friday, March 29 at 12:05 pm. Months ago I booked us one way train tickets to Freiburg on the 1:51 train, but it seems our train has been canceled - at least that’s my interpretation of the notification I received from DB. The note also seems to indicate that our tickets will be valid on any other train making that journey. Is that correct? Thanks for any guidance offered. It is appreciated.

Essentially, yes that's how I read it. But it doesn't mean wait until the day of travel to rebook. You should decide which itinerary you want to take and go through the rebooking process to see if it works.

The only options I see are for the same itinerary departing at 12:51 (which you may or may not be able to catch), then the 14:51 or 16:51 all connecting in Mannheim.

You should look to see if you can piece together 2 separate itineraries - FRA to Mannheim, then Mannheim to Freiburg.
Rather than wait at FRA, I'd take the 1st available train to Mannheim, and wait there if I had to...

IC 107 Frankfurt airport dp 13.51 will run up to Karlsruhe only.
Theoretically you could go from there by regional trains first to Offenbuerg, then to Freiburg ar 16.06
If you leave the FRA airport at 14.51, you have only 1 train change and reach Ffreiburg only ay few minutes laer.

Thanks for the info. It seems like the simplest thing to do would be to just board whatever train that works (and I definitely prefer waiting for the later train that is more direct) with our existing tickets. Seems easier than paying for another set of tickets and then needing to request a refund for the journey that was canceled. Does anyone have experience with this? Should I make seat reservations for the new train? I don’t believe I originally had those. We’re traveling on Good Friday which may be a big holiday weekend travel day.