boot -t iso9660 sr0:kernels/generic.gz root=/dev/sr0

hangs after giving two lines of #####...

No response after that. This is similar to what happened
when the system was booted with the wrong kernel under 5.1
[I'm trying to upgrade. But if the kernel won't boot,
where are things supposed to go?]

Ideally, i'd like to be able to do something like this:
boot sda2:ruffian.gz root=/dev/sr0

And i've tried that, using the old ruffian.gz kernel from
5.1, but it kernel panics trying to mount the cdrom.

I'd prefer a new kernel image to go with the architecture
if at all possible (or just the correct magic to give milo).
My floppy drive is flaky, so creating and using boot
floppies. [It's easier and more reliable to burn CDs...]