After upgrading a Shopware project to 6.7.11.1, the Administration can fail to load with this 500 Internal Server Error:

The Administration fails to load with a 500 Internal Server Error:
An exception has been thrown during the rendering of a template ("Shopware\Core\Framework\Adapter\Twig\Extension\TwigFeaturesWithInheritanceExtension::include(): Return value must be of type string, Twig\Markup returned") in "@Administration/administration/index.html.twig" at line 11.

My first recommendation is to update further to Shopware 6.7.12.x if your project, plugins, apps, PHP version, and deployment window allow it. A patch release is usually the cleaner path than staying on a problematic patch version.

If you cannot move to 6.7.12.x yet, add the official Shopware conflicts repository and require the conflicts package:

composer config repositories.shopware-conflicts composer https://shopware.github.io/conflicts/
composer require shopware/conflicts

After that, run your normal update flow again, for example composer update or your project-specific deployment/update command.

The package does not replace a real compatibility check for plugins, apps, custom code, or PHP versions. What it does is give Composer extra conflict rules from Shopware so incompatible package versions are rejected earlier during dependency resolution.

I like adding this as a small safety step during Shopware updates because it makes the Composer result easier to trust before moving the update through staging and production.