我是 Kubuntu 新手。当我尝试安装 pspp 时出现此错误：sudo apt-get install pspp
结果是：
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package pspp 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: Package 'pspp' has no installation candidate
sudo apt update
Hit:1 http://ir.archive.ubuntu.com/ubuntu focal InRelease
Hit:2 http://ir.archive.ubuntu.com/ubuntu focal-updates InRelease
Get:3 http://archive.ubuntu.com/ubuntu focal InRelease [265 kB]
Hit:4 http://ir.archive.ubuntu.com/ubuntu focal-backports InRelease
Hit:5 http://security.ubuntu.com/ubuntu focal-security InRelease
Get:6 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages [970 kB]
Get:7 http://archive.ubuntu.com/ubuntu focal/main i386 Packages [718 kB]
Get:8 http://archive.ubuntu.com/ubuntu focal/main Translation-en [506 kB]
Get:9 http://archive.ubuntu.com/ubuntu focal/main amd64 DEP-11 Metadata [494 kB]
Get:10 http://archive.ubuntu.com/ubuntu focal/main DEP-11 48x48 Icons [98.4 kB]
Get:11 http://archive.ubuntu.com/ubuntu focal/main DEP-11 64x64 Icons [163 kB]
Get:12 http://archive.ubuntu.com/ubuntu focal/main DEP-11 64x64@2 Icons [15.8 kB]
Get:13 http://archive.ubuntu.com/ubuntu focal/main DEP-11 128x128 Icons [367 kB]
Get:14 http://archive.ubuntu.com/ubuntu focal/main amd64 c-n-f Metadata [29.5 kB]
Get:15 http://archive.ubuntu.com/ubuntu focal/universe amd64 Packages [8,628 kB]
Get:15 http://archive.ubuntu.com/ubuntu focal/universe amd64 Packages [8,628 kB]
Hit:17 https://packages.microsoft.com/repos/edge stable InRelease
Get:18 http://archive.ubuntu.com/ubuntu focal/universe Translation-en [5,124 kB]
Get:19 http://archive.ubuntu.com/ubuntu focal/universe amd64 DEP-11 Metadata [3,603 kB]
Get:20 http://archive.ubuntu.com/ubuntu focal/universe DEP-11 48x48 Icons [3,016 kB]
Get:21 http://archive.ubuntu.com/ubuntu focal/universe DEP-11 64x64 Icons [7,794 kB]
Get:22 http://archive.ubuntu.com/ubuntu focal/universe DEP-11 64x64@2 Icons [44.3 kB]
Get:23 http://archive.ubuntu.com/ubuntu focal/universe DEP-11 128x128 Icons [14.3 MB]
Get:24 http://archive.ubuntu.com/ubuntu focal/universe amd64 c-n-f Metadata [265 kB]
Fetched 40.3 MB in 1min 17s (524 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 20.04.3 LTS
Release: 20.04
Codename: focal
grep -r deb /etc/apt/sources.list /etc/apt/sources.list.d/
/etc/apt/sources.list:# deb cdrom:[Kubuntu 20.04.3 LTS _Focal Fossa_ - Release amd64 (20210819.1)]/ focal main multiverse restricted universe
/etc/apt/sources.list:deb http://ir.archive.ubuntu.com/ubuntu/ focal main restricted
/etc/apt/sources.list:# deb-src http://ir.archive.ubuntu.com/ubuntu/ focal main restricted
/etc/apt/sources.list:deb http://ir.archive.ubuntu.com/ubuntu/ focal-updates main restricted
/etc/apt/sources.list:# deb-src http://ir.archive.ubuntu.com/ubuntu/ focal-updates main restricted
/etc/apt/sources.list:deb http://ir.archive.ubuntu.com/ubuntu/ focal universe
/etc/apt/sources.list:# deb-src http://ir.archive.ubuntu.com/ubuntu/ focal universe
/etc/apt/sources.list:deb http://ir.archive.ubuntu.com/ubuntu/ focal-updates universe
/etc/apt/sources.list:# deb-src http://ir.archive.ubuntu.com/ubuntu/ focal-updates universe
/etc/apt/sources.list:deb http://ir.archive.ubuntu.com/ubuntu/ focal multiverse
/etc/apt/sources.list:# deb-src http://ir.archive.ubuntu.com/ubuntu/ focal multiverse
/etc/apt/sources.list:deb http://ir.archive.ubuntu.com/ubuntu/ focal-updates multiverse
/etc/apt/sources.list:# deb-src http://ir.archive.ubuntu.com/ubuntu/ focal-updates multiverse
/etc/apt/sources.list:deb http://ir.archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse
/etc/apt/sources.list:# deb-src http://ir.archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse
/etc/apt/sources.list:# deb http://archive.canonical.com/ubuntu focal partner
/etc/apt/sources.list:# deb-src http://archive.canonical.com/ubuntu focal partner
/etc/apt/sources.list:deb http://security.ubuntu.com/ubuntu focal-security main restricted
/etc/apt/sources.list:# deb-src http://security.ubuntu.com/ubuntu focal-security main restricted
/etc/apt/sources.list:deb http://security.ubuntu.com/ubuntu focal-security universe
/etc/apt/sources.list:# deb-src http://security.ubuntu.com/ubuntu focal-security universe
/etc/apt/sources.list:deb http://security.ubuntu.com/ubuntu focal-security multiverse
/etc/apt/sources.list:# deb-src http://security.ubuntu.com/ubuntu focal-security multiverse
/etc/apt/sources.list:# (e.g. netinst, live or single CD). The matching "deb cdrom"
/etc/apt/sources.list:deb http://archive.ubuntu.com/ubuntu focal main universe
/etc/apt/sources.list:# deb-src http://archive.ubuntu.com/ubuntu focal main universe
/etc/apt/sources.list.d/microsoft-edge.list.save:deb [arch=amd64] https://packages.microsoft.com/repos/edge/ stable main
/etc/apt/sources.list.d/microsoft-edge.list:deb [arch=amd64] https://packages.microsoft.com/repos/edge/ stable main