The original title is: chiark’s skip-skip-cross-up-grade
Since that isn't very informative, I tried to simplify the first sentence: Two weeks ago I upgraded chiark from Debian jessie i386 to bullseye amd64, after nearly 30 years running Debian i386. This went really quite well, in fact!
Realizing now the feet is going from i386 to amd64, rather than an old debian version upgrade.