The content in 90-local.conf here is meant only to shrink the size of initrds by omitting content that a multibooting environment makes pointless to waste space including — whatever causes a new kernel and/or initrd to prevent booting can be fixed by booting something else if booting an older kernel/initrd won’t do it.
I just added the causal 01-dist.conf to another TW host (gb970), dup’d to 20260531, installed another kernel, and the (expected) result was initramfs-<ver> only instead of initrd-<ver> plus vmlinuz and initrd symlinks.
The solution is obvious, scrapping the un-owned ancient .conf file, but not why naming of the initrd initramfs instead, the apparent reason for symlink creation failure, could result from its content.