我不得不绕了好远才能获得 Steam，因为我遇到了错误 403 Forbidden。我解决了这个问题，但当 Steam 启动时，我被告知它想要添加其他文件。当我单击该应用程序时，我收到一条消息，建议我安装这些文件。运行时，我在控制台中看到以下对话框：
>Steam needs to install these additional packages:
> libgl1-mesa-dri:i386, libgl1-mesa-glx:i386, libc6:i386
>[sudo] password for robert:
>.............................................................................>.............................................................................>.............................................................................>.............W: The repository 'cdrom://Ubuntu-MATE 16.04.1 LTS _Xenial >Xerus_ - Release powerpc (20160719) xenial Release' does not have a Release >file.
>E: Failed to fetch cdrom://Ubuntu-MATE 16.04.1 LTS _Xenial Xerus_ - Release >powerpc (20160719)/dists/xenial/main/binary-powerpc/Packages Please use >apt-cdrom to allow APT to recognise this CD-ROM. 'apt-get update' cannot be >used to add new CD-ROMs
>E: Failed to fetch http://gb.ports.ubuntu.com/ubuntu-ports/dists/xenial>/main/binary-i386/Packages 404 Not Found [IP: 2001:67c:1360:8001::22 80]
>E: Failed to fetch http://gb.ports.ubuntu.com/ubuntu-ports/dists/xenial->updates/main/binary-i386/Packages 404 Not Found [IP: >2001:67c:1360:8001::22 80]
財政部
E: Some index files failed to download. They have been ignored, or old ones used instead.
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package libc6:i386 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
libdb1-compat initscripts tzdata
Package libgl1-mesa-glx:i386 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Unable to locate package libgl1-mesa-dri:i386
E: Package 'libgl1-mesa-glx:i386' has no installation candidate
E: Package 'libc6:i386' has no installation candidate
Press return to cont
有人能给点建议吗？我正在运行 G5 PowerMac，运行 ubintu-MATE 16.04。有什么想法可以让它工作吗？