Correct way to change core module code

Question

I have one line of code in a core module (contact) in which I need to change. What is the correct way to make the change to change/overwrite this file?

Answer 1

There are two ways to do that:

1. You can use composer patches to change file (https://github.com/cweagans/composer-patches)
2. Use around plugin to override specific public method on a class. (https://devdocs.magento.com/guides/v2.3/extension-dev-guide/plugins.html)

Answer 2

You can override using magento plugin concept or simply override concept using preferences