dockerに作成したubuntu22.04のgpgエラーを解消したい

前提・実現したいこと

wsl2上のUbuntu20.04のdockerにUbuntu22.04を構築したい。

行ったこと

docker image pull ubuntu:22.04でプルしたイメージからコンテナを作成した。
コンテナを起動し、echoのリダイレクトで/etc/apt/apt.confにproxyの設定を記述した。

発生している問題・エラーメッセージ

apt updateを実行したところgpgエラーが発生した。(次項目)
そこで次の操作を行いました。

root@42557a547a4e:/# apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 871920D1991BC93C
E: gnupg, gnupg2 and gnupg1 do not seem to be installed, but one of them is required for this operation
root@42557a547a4e:/# apt install gnupg
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package gnupg 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 'gnupg' has no installation candidate

apt updateを実行するにはgpgエラーを解消しなければならず、
gpgエラーを解消するにはgnupgをインストールしなければならず、
gnupgをインストールするには(おそらく)apt updateを実行しなければならないと思うのですが
どうしたらうまくいきますか？

gpgエラー内容

root@42557a547a4e:/# apt update
Get:1 http://archive.ubuntu.com/ubuntu jammy InRelease [270 kB]
Err:1 http://archive.ubuntu.com/ubuntu jammy InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
Get:2 http://security.ubuntu.com/ubuntu jammy-security InRelease [110 kB]
Err:2 http://security.ubuntu.com/ubuntu jammy-security InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
Get:3 http://archive.ubuntu.com/ubuntu jammy-updates InRelease [114 kB]
Err:3 http://archive.ubuntu.com/ubuntu jammy-updates InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
Get:4 http://archive.ubuntu.com/ubuntu jammy-backports InRelease [99.8 kB]
Err:4 http://archive.ubuntu.com/ubuntu jammy-backports InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
Reading package lists... Done
W: http://archive.ubuntu.com/ubuntu/dists/jammy/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2012-cdimage.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: http://archive.ubuntu.com/ubuntu/dists/jammy/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2018-archive.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: GPG error: http://archive.ubuntu.com/ubuntu jammy InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
E: The repository 'http://archive.ubuntu.com/ubuntu jammy InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: http://security.ubuntu.com/ubuntu/dists/jammy-security/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2012-cdimage.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: http://security.ubuntu.com/ubuntu/dists/jammy-security/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2018-archive.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: GPG error: http://security.ubuntu.com/ubuntu jammy-security InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
E: The repository 'http://security.ubuntu.com/ubuntu jammy-security InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: http://archive.ubuntu.com/ubuntu/dists/jammy-updates/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2012-cdimage.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: http://archive.ubuntu.com/ubuntu/dists/jammy-updates/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2018-archive.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: GPG error: http://archive.ubuntu.com/ubuntu jammy-updates InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
E: The repository 'http://archive.ubuntu.com/ubuntu jammy-updates InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: http://archive.ubuntu.com/ubuntu/dists/jammy-backports/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2012-cdimage.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: http://archive.ubuntu.com/ubuntu/dists/jammy-backports/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg.d/ubuntu-keyring-2018-archive.gpg are ignored as the file is not readable by user '_apt' executing apt-key.
W: GPG error: http://archive.ubuntu.com/ubuntu jammy-backports InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
E: The repository 'http://archive.ubuntu.com/ubuntu jammy-backports InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Problem executing scripts APT::Update::Post-Invoke 'rm -f /var/cache/apt/archives/*.deb /var/cache/apt/archives/partial/*.deb /var/cache/apt/*.bin || true'
E: Sub-process returned an error code