How to use User Stylesheets to customize the style of some websites, without using a third party browser extension?

Question

I know the Stylus and Stylish (not recommended) browser extensions that can re-style a given website (basically by customizing CSS).

In this comment , the author states this can be done via "user stylesheets".

How is it possible to use "user stylesheets" to modify the style of www.example.com and a different style for www.example2.com?

Is it something that can be done without requiring a third-party browser extension, if so, how/where in the browser options should we add our custom CSS?

Answer 1

This seems to be deprecated nowadays:

https://codereview.chromium.org/66383005/

Remove the concept of user stylesheets.
-The support for this has been removed from Chromium already.
This is now just deleting dead code.
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