Well my friend, you've come to the right place at the right time.
I have installed Ubuntu 6.10 on my powerpc64. No other versions would install right. Now that it is installed I get loud fan noise which is really annoying.
Is there a newer version of Ubuntu that I can use?
Does anyone know how to stop the fan noise?
That fan problem you have on Ubuntu 6.06 "Dapper Drake" is due to the fact that
the kernel that comes installed with that version has no "thermal control" (fan control)
I agree with you completely that "Dapper" is/was the only version of Ubuntu that would install "properly" as it was "properly" supported for the PPC architecture.
The good news is that Ubuntu 8.04 "Hardy Heron" has just been officially released today !
Though there is no "official" PPC support, there is a PPC installer for your machine.
However, I have some bad news for you.
I would be losing the respect of my comrades here on the Ubuntu Forum if I did not flame you repeatedly for not conducting a proper "search" of the forums to find the answers you have requested. There are an almost infinite amount of references to your issue.
Apparently, I am also not "allowed" to tell you where the PPC Ubuntu Hardy Install ISO images reside but I am sure a "proper" Google search will yield the result for which you are looking.
hardy heron ppc installer