AFAIR the CT60 came with a patched version of
ataboot/bootstrap that would have contained the cache flush patch.
That's true but as mentioned, it wouldn't let you boot anything which requires more than ~6.5 MB of ST RAM for the staging area.
The CT60 web pages
appear to have gone away - can't check what version could be
downloaded there anymore.
Does the installer find the IDE disk drive at all? I wonder if
the ISO scanning issues are down to the kernel using a different
host adapter driver (pata_falcon, not falconide) these days?
I wanted to post a separate email about it but since you have asked... ;) No, it doesn't (at least the image with 6.6.15 I tried). I had to extract and inject libata.ko.xz + pata_falcon.ko.xz from cdrom to hd-media initrd.gz, that made /dev/sda accessible. However not mountable because it seems that the kernel doesn't contain modules for msdosfs? So that's another task to tick off.