How to fix «Argument 1 passed to Magento\Framework\Model\ResourceModel\Db\AbstractDb::load() must be an instance of Magento\Framework\Model\AbstractModel, string given,called in vendor/amzn/amazon-payments-magento-2-plugin»?

To fix the issue, remove the amzn/amazon-payments-magento-2-plugin package:

composer remove amzn/amazon-payments-magento-2-plugin

Then re-compile the Magento’s code.

github.com/amzn/amazon-payments-magento-2-plugin/issues/360#issuecomment-430250971