ご回答いただきありがとうございます。

PHPのバージョンを変更して試してみましたがまた新しいエラーが発生しました。
このエラーは以前別のスレッドで似たようなものを見たことがあったので下のサイトを参考にsodiumをインストールしてみましたが、エラーが発生しました。

https://www.kcapps.net/%E3%83%AC%E3%83%B3%E3%82%BF%E3%83%AB%E3%82%B5%E3%83%BC%E3%83%90%E3%83%BC/%E3%81%95%E3%81%8F%E3%82%89%E3%82%A4%E3%83%B3%E3%82%BF%E3%83%BC%E3%83%8D%E3%83%83%E3%83%88%E3%81%AE%E3%83%AC%E3%83%B3%E3%82%BF%E3%83%AB%E3%82%B5%E3%83%BC%E3%83%90%E3%83%BC%E3%81%ABsodium%E6%8B%A1/

インストールしたフォルダは以下となります。

さくらのサーバー
|
|-EC-CUBEのフォルダ
|
|-sodliumをインストールしたフォルダ(上記サイトのworkspace)

環境につきましては最初の投稿と同じです。

ここから先がインストール確認のログ確認で出力したエラーです。

**************** SoftbankPayment42 ****************
<warning>A script named compile would override a Composer command and has been skipped</warning>
<warning>A script named auto-scripts would override a Composer command and has been skipped</warning>
<warning>A script named installer-scripts would override a Composer command and has been skipped</warning>
[6.7MiB/1.02s] Using version ^4.2 for ec-cube/softbankpayment42
[6.7MiB/1.02s] ./composer.json has been updated
[8.2MiB/1.14s] Running composer update ec-cube/softbankpayment42 --with-dependencies
[11.2MiB/1.17s] Loading composer repositories with package information
[12.1MiB/2.21s] <warning>Dependency ec-cube/plugin-installer is also a root requirement. Package has not been listed as an update argument, so keeping locked at old version. Use --with-all-dependencies (-W) to include root dependencies.</warning>
[12.4MiB/2.25s] Updating dependencies
[14.2MiB/2.30s] Your requirements could not be resolved to an installable set of packages.
[14.2MiB/2.30s]
Problem 1
- lcobucci/jwt 4.2.1 requires ext-sodium * -> it is missing from your system. Install or enable PHP's sodium extension.
- league/oauth2-server-bundle v0.3.0 requires league/oauth2-server ^8.3 -> satisfiable by league/oauth2-server[8.3.5].
- ec-cube/api42 4.2.3 requires league/oauth2-server-bundle ^0.3 -> satisfiable by league/oauth2-server-bundle[v0.3.0].
- league/oauth2-server 8.3.5 requires lcobucci/jwt ^3.4.6 || ^4.0.4 -> satisfiable by lcobucci/jwt[4.2.1].
- ec-cube/api42 is locked to version 4.2.3 and an update of this package was not requested.

To enable extensions, verify that they are enabled in your .ini files:
- /usr/local/php/8.1/etc/php.ini
- /usr/local/php/8.1/etc/conf.d/apcu.ini
- /usr/local/php/8.1/etc/conf.d/imagick.ini
- /usr/local/php/8.1/etc/conf.d/mcrypt.ini
- /usr/local/php/8.1/etc/conf.d/opcache.ini
- /home/masatomiplan/.php.config/php.ini
You can also run `php --ini` in a terminal to see which files are used by PHP in CLI mode.
Alternatively, you can run Composer with `--ignore-platform-req=ext-sodium` to temporarily ignore these required extensions.
[14.2MiB/2.30s] <warning>Running update with --no-dev does not mean require-dev is ignored, it just means the packages will not be installed. If dev requirements are blocking the update you have to resolve those problems.</warning>
[12.8MiB/2.30s] You can also try re-running composer require with an explicit version constraint, e.g. "composer require ec-cube/SoftbankPayment42:*" to figure out if any version is installable, or "composer require ec-cube/SoftbankPayment42:^2.1" if you know which you need.
[12.8MiB/2.30s]
Installation failed, reverting ./composer.json and ./composer.lock to their original content.
[12.7MiB/2.30s] Memory usage: 12.71MiB (peak: 14.63MiB), time: 2.3s

{"success":false,"log":"\u003Cwarning\u003EA script named compile would override a Composer command and has been skipped\u003C\/warning\u003E\n\u003Cwarning\u003EA script named auto-scripts would override a Composer command and has been skipped\u003C\/warning\u003E\n\u003Cwarning\u003EA script named installer-scripts would override a Composer command and has been skipped\u003C\/warning\u003E\n[6.7MiB\/1.02s] Using version ^4.2 for ec-cube\/softbankpayment42\n[6.7MiB\/1.02s] .\/composer.json has been updated\n[8.2MiB\/1.14s] Running composer update ec-cube\/softbankpayment42 --with-dependencies\n[11.2MiB\/1.17s] Loading composer repositories with package information\n[12.1MiB\/2.21s] \u003Cwarning\u003EDependency ec-cube\/plugin-installer is also a root requirement. Package has not been listed as an update argument, so keeping locked at old version. Use --with-all-dependencies (-W) to include root dependencies.\u003C\/warning\u003E\n[12.4MiB\/2.25s] Updating dependencies\n[14.2MiB\/2.30s] Your requirements could not be resolved to an installable set of packages.\n[14.2MiB\/2.30s] \n Problem 1\n - lcobucci\/jwt 4.2.1 requires ext-sodium * -\u003E it is missing from your system. Install or enable PHP\u0027s sodium extension.\n - league\/oauth2-server-bundle v0.3.0 requires league\/oauth2-server ^8.3 -\u003E satisfiable by league\/oauth2-server[8.3.5].\n - ec-cube\/api42 4.2.3 requires league\/oauth2-server-bundle ^0.3 -\u003E satisfiable by league\/oauth2-server-bundle[v0.3.0].\n - league\/oauth2-server 8.3.5 requires lcobucci\/jwt ^3.4.6 || ^4.0.4 -\u003E satisfiable by lcobucci\/jwt[4.2.1].\n - ec-cube\/api42 is locked to version 4.2.3 and an update of this package was not requested.\n\nTo enable extensions, verify that they are enabled in your .ini files:\n - \/usr\/local\/php\/8.1\/etc\/php.ini\n - \/usr\/local\/php\/8.1\/etc\/conf.d\/apcu.ini\n - \/usr\/local\/php\/8.1\/etc\/conf.d\/imagick.ini\n - \/usr\/local\/php\/8.1\/etc\/conf.d\/mcrypt.ini\n - \/usr\/local\/php\/8.1\/etc\/conf.d\/opcache.ini\n - \/home\/masatomiplan\/.php.config\/php.ini\nYou can also run `php --ini` in a terminal to see which files are used by PHP in CLI mode.\nAlternatively, you can run Composer with `--ignore-platform-req=ext-sodium` to temporarily ignore these required extensions.\n[14.2MiB\/2.30s] \u003Cwarning\u003ERunning update with --no-dev does not mean require-dev is ignored, it just means the packages will not be installed. If dev requirements are blocking the update you have to resolve those problems.\u003C\/warning\u003E\n[12.8MiB\/2.30s] You can also try re-running composer require with an explicit version constraint, e.g. \u0022composer require ec-cube\/SoftbankPayment42:*\u0022 to figure out if any version is installable, or \u0022composer require ec-cube\/SoftbankPayment42:^2.1\u0022 if you know which you need.\n[12.8MiB\/2.30s] \nInstallation failed, reverting .\/composer.json and .\/composer.lock to their original content.\n[12.7MiB\/2.30s] Memory usage: 12.71MiB (peak: 14.63MiB), time: 2.3s\n"}

皆様何とぞお力添えいただければ幸いです。