I need relevant.xml file for
<checkout_onepage_index> in Magento 1 to Magento 2?
In Magento 2, the action handle checkout_onepage_index has been changed to checkout_index_index.
Also, Magento 2 has split the layout files based on layout handle. So, you can find equivalent layout file named as
This file can be in many different modules since any module can change/modify the layout of any other module's action in Magento 2.