I can't find a working download link for Toon Artist Action Set.

Looking at some of the comments on the Behance page, it seems this plug-in has been missing in action for a good few years now - presumably one of the Photoshop updates rendered it nonfunctional, and BlackNull/Nuwan Panditha hasn’t updated yet…

I also note that his DeviantArt link is out of date - they stopped giving members [username].deviantart.com URLs several years ago - and his last YouTube video was uploaded three years ago, so it’s entirely possible Nuwan himself is MIA.

There’s lots of info, but the link on the Behance page is not function, as you said.  It’s not entirely clear who the author is either, but if you work that out, then contact directly

[Free] Toon Artist - Photoshop Action :: Behance

It looks interesting, so please let us know if you find a working link.

I found no such action as Toon Artist on Creative Cloud (“Page not found”)…

A web search for “Toon Artist photoshop action” came up with

https://www.behance.net/gallery/102056881/Free-Toon-Artist-Photoshop-Action#

I saw other similarly-named actions in my search, on third-party, use-at-your-own risk sites.