What is a proper way to implement offline payment method in Magento 2.2.*?
I did it old style like in module magento/module-offline-payments and it is working.
My payment model extends Magento\Payment\Model\Method\AbstractMethod.
I wonder that Magento\Payment\Model\Method\AbstractMethod is deprecated and a suggestion is that custom payment method should extend Magento\Payment\Model\Method\Adapter but I don't want to make integration with any payment provider gateway.
In Magento 2 guides I found only integration with the third-party approach:
https://devdocs.magento.com/guides/v2.2/payments-integrations/bk-payments-integrations.html
Sample:
https://github.com/magento/magento2-samples/tree/master/sample-module-payment-gateway