Apparently yaboot does not get installed in MintPPC 11. You could try to do it manually, by skipping the yaboot installation and just continue with the last steps of the installation. Yaboot can be installed from a 'rescue' session from a Debian Squeeze installation CD.
if you want to try the latter, boot the Squeeze CD with the following option:
and have yaboot installed.
@JD: Personally, IMHO, I don't think there is a general problem with Yaboot not being installed in 11, in each of my three failed installations on the iMac (G4!!!) Yaboot has been installed; I think either the problem is that Debian doesn't know how to run desktop/iMac . . . or they aren't recognizing PPC??? computers???? . . . that is the only conclusion(s) that I can surmise . . . . : - )))) The latest attempt from a couple of Sundays back has probably been the "worst" installation yet, giving me only the Yaboot prompt and quickly moving to a kernel panic . . . . Trying "Linux 1" also leads not to TTY, but to again with the kernel panic . . . haven't had time to try to "rescue" the installation, but even though "hope springs eternal" I don't have high expectation for that actually fixing the problem . . . . In actually trying to understand the phrase "Google is your friend" I did find a thread from late 2011 that was cross posted to the other mac/linux forum by JD, someone was (as did Omeluuck) saying that they had traced the problem to the "initrd" "file"??? (is that the right word?) in the installation/installer . . . and in doing the "expert" installation the choice is presented to me to do something with it, but I, not being an expert, simply went with the default choice . . . whatever that was . . . resulting in a kernel panic OS. Ojordan has posted requesting that I post my "logs" from that installation and have yet to have time to do that, maybe later today I'll get the chance. Point being, there has been a problem getting Debian installed on, perhaps especially iMacs for quite some time without it being addressed or "fixed" . . . and appears to have serendipitous outcomes . . . like gambling, sometimes you win, but the house rules the day. : - 0