We're going to try again...
As described here under Europe Regions (either this category hadn't been created or I missed it), we were booked on Yuletide Spirit for December 2020:
We are going to try again for the December 6, 2022, southbound cruise from Amsterdam to Brussels. Anybody else?
P.S. Hard to think of this as a Rhine River cruise (per category), but there is some intersection at Rotterdam.