我最近刚刚在我的 Raspberry Pi 上安装了 32 位版本的 Ubuntu Server 20.04，主要是为了设置反恐精英服务器。我尝试安装 SteamCMD，但它给了我一个错误，提示：
"Package steamcmd 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."
我在网上查阅了一下，有一个网站告诉我应该更新我的 apt，但是我无法更新，因为它给出了这个错误：
Reading package lists... Done
E: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/focal/main/binary-i386/Packages 404 Not Found [IP: 91.189.88.142 80]
E: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/focal-backports/universe/binary-i386/Packages 404 Not Found [IP: 91.189.88.142 80]
E: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/focal-security/main/binary-i386/Packages 404 Not Found [IP: 91.189.88.142 80]
E: Failed to fetch http://ports.ubuntu.com/ubuntu-ports/dists/focal-updates/main/binary-i386/Packages 404 Not Found [IP: 91.189.88.142 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.
所以我被困住了。有人知道如何解决这个问题吗？