SiteAccess Repository Layer helper service eZ\Publish\Core\Repository\SiteAccessAware\Language\LanguageResolver defined as ezpublish.helper.language_resolver, injects dynamic settings too early which might have difficult to debug side-effects in the form of race when resolving dynamic parameters for other services (like cache adapter).

Given dynamic settings are incompatible with Symfony4, the best option right now is to inject ConfigResolver and get languages dynamic parameter only when needed.