Magento 2.4.2 Configurable Product – Fixing VariationMatrix Error

I had the same problem.

After searching the source of Magento 2.2.4 I found the function in file (vendor\magento\module-catalog-inventory\Model\Configuration.php):

public function getDefaultScopeId()
{
    // TODO: should be fixed in MAGETWO-46043
    // "0" is id of admin website, which is used in backed during save entity
    return 0;
}

In my case I modify Store parameters at "Stores > All Stores" and my actual store_id/scope_id was 1 and not 0. After changing "return 0" to "return 1", my problem was solved.

As this is anyhow TODO for Magento I expect, that in next upgrade this will be solved and all my modification will be overwritten and everything should work at that time...

Your environment is using ARGON2ID13 instead of SHA256 for hashing.

Check if you have 'sodium' php extension enabled.

If you disable the libsodium php extension, it will fallback on SHA-256 and won't break Magento.

In the Docker php-fpm image you can comment it out in /usr/local/etc/php/conf.d/docker-php-ext-sodium.ini:

;extension=sodium.so