$ apt list coreutils
Listing... Done
coreutils/unstable,now 8.30-3+b1 amd64 [installed]
coreutils/unstable 8.30-3 arm64
coreutils/unstable 8.30-3 armhf
coreutils/unstable 8.30-3 i386

$ apt list --all-versions coreutils 
Listing... Done
coreutils/unstable,now 8.30-3+b1 amd64 [installed]

coreutils/unstable 8.30-3 arm64

coreutils/unstable 8.30-3 armhf

coreutils/unstable 8.30-3 i386

$ apt list --upgradeable binutils
Listing... Done
binutils/unstable 2.34-7 amd64 [upgradable from: 2.34-6]
N: There is 1 additional version. Please use the '-a' switch to see it
$ apt list --upgradeable -a binutils
Listing... Done
binutils/unstable 2.34-7 amd64 [upgradable from: 2.34-6]
binutils/now 2.34-6 amd64 [installed,upgradable to: 2.34-7]

$ apt list --installed coreutils 
Listing... Done
coreutils/unstable,now 8.30-3+b1 amd64 [installed]

source.listを編集する． テキストエディタを変更したい場合は環境変数 EDITOR を好みのものに変更する．

既定値では /etc/apt/sources.list を編集する．

$ sudo apt edit-sources

健全性チェックを行ってくれるので少し安心．以下は5行目の間違いを指摘してくれている．Y で再度編集． n で間違ったまま編集終了

E: Type 'dev' is not known on line 5 in source list /etc/apt/sources.list
E: The list of sources could not be read.
Failed to parse /etc/apt/sources.list. Edit again?  [Y/n] 

/etc/apt/sources.list.d/ 以下のファイル名を指定するとその source.list ファイルの編集が出来る．以下の例では， /etc/apt/sources.list.d/josm.list

$ sudo apt edit-sources josm.list

apt update で発生したエラー

Err:79 http://ftp.jp.debian.org/debian sid/main amd64 Contents (deb)
  Hash Sum mismatch
  Hashes of expected file:
   - Filesize:40050091 [weak]
   - SHA256:fb5fd482b426bd3bf5968d0ab2f87c3d839963e62991abd75b7a16dbe825fdc8
   - MD5Sum:e0fcbd214b57a1edb11beb389665ec7c [weak]
  Hashes of received file:
   - SHA256:4ec22b6278f2e93e6e072d38979488645a7a9a4a5da06d6a0dd1d79f54835f4a
   - MD5Sum:3849b63d50372f264c2b96ba880f0e58 [weak]
   - Filesize:40050091 [weak]
  Last modification reported: Tue, 12 May 2020 14:06:10 +0000
  Release file created at: Tue, 12 May 2020 14:17:08 +0000

E: Failed to fetch http://ftp.jp.debian.org/debian/dists/sid/main/by-hash/SHA256/fb5fd482b426bd3bf5968d0ab2f87c3d839963e62991abd75b7a16dbe825fdc8
  Hash Sum mismatch
   Hashes of expected file:
    - Filesize:40050091 [weak]
    - SHA256:fb5fd482b426bd3bf5968d0ab2f87c3d839963e62991abd75b7a16dbe825fdc8
    - MD5Sum:e0fcbd214b57a1edb11beb389665ec7c [weak]
   Hashes of received file:
    - SHA256:4ec22b6278f2e93e6e072d38979488645a7a9a4a5da06d6a0dd1d79f54835f4a
    - MD5Sum:3849b63d50372f264c2b96ba880f0e58 [weak]
    - Filesize:40050091 [weak]
   Last modification reported: Tue, 12 May 2020 14:06:10 +0000
   Release file created at: Tue, 12 May 2020 14:17:08 +0000
W: Some index files failed to download. They have been ignored, or old ones used instead.

1日経っても直らなかったので自分の環境を疑う．

間にapt proxy(apt-cacher-ng)がある環境だったのでそれを一時的に使わないようにしたら直った．

$ sudo apt update -o Acquire::http::Proxy=''

cacheが腐っていたよう．

Err:48 https://dl.yarnpkg.com/debian stable InRelease                                                                                           
  The following signatures were invalid: EXPKEYSIG 23E7166788B63E1E Yarn Packaging <yarn@dan.cx>

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https
://dl.yarnpkg.com/debian stable InRelease: The following signatures were invalid: EXPKEYSIG 23E7166788B63E1E Yarn Packaging <yarn@dan.cx>

• Yarn Debian key expiry date updated \(EXPKEYSIG 23E7166788B63E1E\) · Issue \#7866 · yarnpkg/yarn