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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