I do not believe yaboot has in active development in a long time
upstream. The last set of commits were in 2008 see:
https://github.com/pnasrat/yaboot/commits/master

I think we are just stuck with make a separate ext2 /boot partition.

On Wed, Oct 12, 2016 at 12:02 PM, ernsteiswuerfel <email address hidden> wrote:
> Yes, Xenials daily iso of yesterday also worked.
>
> I even tried to get this upstream via <email address hidden> as
> stated on https://lists.ozlabs.org/listinfo/ but there my message sits
> waiting to get approved by the list moderator since 2 weeks...
>
> "Hello!
>
> May I bring this downstream bug reports to your attention:
> https://bugs.launchpad.net/debian/+source/yaboot/+bug/1606089
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=834473
>
> Seems yaboot 'lost' the ability to boot into current (newly formatted)
> ext4 partitions. Booting into ext2 partitions still works.
>
> regards
> Erhard"
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1606089
>
> Title:
>   unable to boot after 'entire disk' install (16.10, ppc)
>
> Status in yaboot package in Ubuntu:
>   Confirmed
> Status in yaboot package in Debian:
>   Confirmed
>
> Bug description:
>   Just did an entire disk install from todays (24.07.2016) Yakkety
>   daily. Installation procedure went fine, but the automatically created
>   /etc/yaboot.conf seems faulty.
>
>   1st stage-boot runs fine, the boot options are displayed correctly,
>   pressing "L" leaves me at the 2nd stage boot prompt where you can
>   choose between "Linux" and "old" boot options. But either of them does
>   not work, throwing the error message:
>
>   "/pci@f4000000/ata-6@d/@0:3,/boot/vmlinux: unknown or corrupt
>   filesystem"
>
>   To rule out other issues I did an openfirmware reset, wiped /dev/sda
>   and tried a second time with a fresh mac partition table. But the
>   problem stays the same, 16.10 is not bootable on my PowerBook 5,6. It
>   did run 16.04 before.
>
>   Partition layout is the standard created by "entire disk" install, /dev/sda4 is swap.
>   /dev/sda2: LABEL="bootstrap" TYPE="hfs" PARTLABEL="untitled"
>   /dev/sda3: UUID="b7bdb9a4-7316-4966-aa65-1d546b211204" TYPE="ext4" PARTLABEL="untitled"
>
>   ## yaboot.conf generated by the Ubuntu installer
>   boot="/dev/disk/by-id/ata-ST9808211A_3LF2VVGH-part2"
>   device=/pci@f4000000/ata-6@d/@0
>   partition=3
>   root="UUID=b7bdb9a4-7316-4966-aa65-1d546b211204"
>   timeout=50
>   install=/usr/lib/yaboot/yaboot
>   magicboot=/usr/lib/yaboot/ofboot
>   enablecdboot
>
>   image=/boot/vmlinux
>         label=Linux
>         read-only
>         initrd=/boot/initrd.img
>         append="quiet splash"
>
>   image=/boot/vmlinux.old
>         label=old
>         read-only
>         initrd=/boot/initrd.img.old
>         append="quiet splash"
>
>   ProblemType: Bug
>   DistroRelease: Ubuntu 16.10
>   Package: yaboot 1.3.16-4ubuntu1
>   ProcVersionSignature: Ubuntu 4.4.0-31.50-powerpc-smp 4.4.13
>   Uname: Linux 4.4.0-31-powerpc-smp ppc
>   ApportVersion: 2.20.2-0ubuntu1
>   Architecture: powerpc
>   CasperVersion: 1.376
>   CurrentDesktop: MATE
>   Date: Mon Jul 25 00:19:21 2016
>   LiveMediaBuild: Ubuntu-MATE 16.10 "Yakkety Yak" - Alpha powerpc (20160724)
>   ProcEnviron:
>    TERM=xterm
>    PATH=(custom, no user)
>    XDG_RUNTIME_DIR=<set>
>    LANG=en_US.UTF-8
>    SHELL=/bin/bash
>   SourcePackage: yaboot
>   UpgradeStatus: No upgrade log present (probably fresh install)
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/ubuntu/+source/yaboot/+bug/1606089/+subscriptions