One useful tool to access older prebuilt binaries is debsnap. It will download recent builds of a given package in a given arch from snapshot.debian.org, for example:
debsnap --binary -a ppc64 libavcodec58
It looks like it downloads the most recent build it can find
first, and then AFAICT, it will just keep on going until it runs
out of binaries to download. I usually Control-C it after one or
two binaries have been downloaded. That is more efficient than
what I have been doing so far at least.
Another useful tool for managing the snapshot.debian.org archives appears to be metasnap. According to this:
https://lists.debian.org/debian-snapshot/2021/01/msg00002.html
You can post up a buildinfo file to metasnap and it will give you a distilled list of archive snapshots that you add to sources.list to fulfill the package's needs.
However, when I tried it, I could not as yet get it to work properly... I'll report back if I sort out how to make that work.
Ken
When trying to install packages for both the 32bit and 64bit powerpc version of debian sid, it is pretty common to find a situation where the package can't be installed due to a missing supporting library.
The latest examples I came across were installing vlc, ffmpeg, firefox, and thunderbird, all of which installed but all of which had several libraries that couldn't be automatically resolved and required manual intervention.
Adrian already put up an explanation for why this happens.
To work around this, I have been going to the snapshot.debian.org web page, and entering the name of the library package that is needed in the appropriate search box. That brings up a list of recent snapshots, and browsing that list has (in most cases) led me to the last ppc or ppc64 version available. I download the deb and install it manually with "dpkg -i ./my_deb.deb" and move on to the next one, until they are all satisfied, and then the package I want installs.
So far this works, but it's somewhat tedious. There are instructions on the snapshot.debian.org web page for adding snapshots to the sources.list , with an over-ride so they are not considered expired, but I'm not clear on how that would work exactly. There are dozens and dozens (hundreds, really) of snapshots. Would one add a snapshot from say a year ago, and ride with that? Or add multiple snapshots? The logic of how those get used in sources.list is not clear to me.
What I'm hoping for is that apt will find and use the latest snapshot version of the needed library on it's own, if that is at all possible, without my "manual" method being needed.
Thanks, anyone who knows how this is supposed to work.
Ken