何故これで上手く行ったかは正直分からないが
同じハマり方した人が１人でも幸せな人生を歩めますよう・・・

件のエラー

Carbon 1 is deprecated, see how to migrate to Carbon 2.
https://carbon.nesbot.com/docs/#api-carbon-2
    You can run './vendor/bin/upgrade-carbon' to get help in updating carbon and other frameworks and libraries that depend on it.
100 packages you are using are looking for funding.
Use the `composer fund` command to find out more!

Run composer recipes at any time to see the status of your Symfony recipes.

Executing script cache:clear --no-warmup [KO]
 [KO]
Script cache:clear --no-warmup returned with error code 255
!!
!!  Fatal error: Could not check compatibility between Symfony\Bridge\ProxyManager\LazyProxy\PhpDumper\LazyLoadingValueHolderGenerator::generate(ReflectionClass $originalClass, Zend\Code\Generator\ClassGenerator $classGenerator) and ProxyManager\ProxyGenerator\LazyLoadingValueHolderGenerator::generate(ReflectionClass $originalClass, Laminas\Code\Generator\ClassGenerator $classGenerator), because class Zend\Code\Generator\ClassGenerator is not available in /Users/tentatsu/src/ohenz4/eccube/vendor/symfony/proxy-manager-bridge/LazyProxy/PhpDumper/LazyLoadingValueHolderGenerator.php on line 25
!!  PHP Fatal error:  Could not check compatibility between Symfony\Bridge\ProxyManager\LazyProxy\PhpDumper\LazyLoadingValueHolderGenerator::generate(ReflectionClass $originalClass, Zend\Code\Generator\ClassGenerator $classGenerator) and ProxyManager\ProxyGenerator\LazyLoadingValueHolderGenerator::generate(ReflectionClass $originalClass, Laminas\Code\Generator\ClassGenerator $classGenerator), because class Zend\Code\Generator\ClassGenerator is not available in /Users/tentatsu/src/ohenz4/eccube/vendor/symfony/proxy-manager-bridge/LazyProxy/PhpDumper/LazyLoadingValueHolderGenerator.php on line 25
!!
!!  In LazyLoadingValueHolderGenerator.php line 25:
!!
!!    Compile Error: Could not check compatibility between Symfony\Bridge\ProxyMa
!!    nager\LazyProxy\PhpDumper\LazyLoadingValueHolderGenerator::generate(Reflect
!!    ionClass $originalClass, Zend\Code\Generator\ClassGenerator $classGenerator
!!    ) and ProxyManager\ProxyGenerator\LazyLoadingValueHolderGenerator::generate
!!    (ReflectionClass $originalClass, Laminas\Code\Generator\ClassGenerator $cla
!!    ssGenerator), because class Zend\Code\Generator\ClassGenerator is not avail
!!    able
!!
!!
!!
Script @auto-scripts was called via post-update-cmd
composer/package-versions-deprecated: Generating version class...
composer/package-versions-deprecated: ...done generating version class
composer/package-versions-deprecated: Generating version class...
composer/package-versions-deprecated: ...done generating version class

１つも意味が分からん。

Composer バージョン２にアップ

composer バージョン1だとgithubのトークンを正しく入れてるのにこんなエラーが出る。

tentatsu@ip-192-168-30-10 eccube % composer install


  [UnexpectedValueException]
  Your github oauth token for github.com contains invalid characters: "ghp_40B**********zdGs"

バージョン２にアップ

composer self-update

composer installしてみる

composer install

上の方に書いた、１つも分からんエラーが出る。

エラーに書かれていたコマンドを実行してみる。

./vendor/bin/upgrade-carbon

するとエラーは出ませんでした。素直にぬるっと実行された。

でもまだエラーが出るのでググったらコレがいいって書かれていた。

composer require laminas/laminas-zendframework-bridge

そしたら無事動きましたとさ。
何の手応えも無い。。。