Hi,
There is currently no built-in Google Ads tag in Matomo Tag Manager.
A long time ago when MTM came out I implemented a basic Tag for Google Ads, but I am unable to test if it works as I don’t use Google Ads and no one else has yet tested it.
So if you are more familiar with Google Ads, could you try adding the tag (adding the three files and few lines in lang/en.json should be enought to add it) and report back how it works so that it can be added to Matomo Tag Manager.
This should work too, but is of course less user-friendly as a “real” tag.
I’m assuming that this is just because the docs explain how MTM works and not how the code of third parties works (as Matomo doesn’t have any control over them)