# Get lenient.
composer require mglaman/composer-drupal-lenient
# Add the module to the allow list. Use escapes for the quote signs. \" ... \"
composer config --merge --json extra.drupal-lenient.allowed-list '[\"drupal/module_with_incompatible_core_version\"]'
# You can check if the merge worked, either just take a look
# into the composer.json or use this command.
composer config --merge --json extra.drupal-lenient.allowed-list
When working with composer you will have multiple lock files. The composer.lock in your application root directory and a installed.json file inside the vendor/composer directory.