according the comments

Author: franzholz

Documentation/Setup/UseStyleguide.rst

@@ -32,8 +32,8 @@ allows to test many TCA related configurations easily, without the need to
 create custom extensions to reproduce problems.
 
 `EXT:styleguide` has been integrated to the TYPO3 Core monorepository with
-version 13. On older TYPO3 versions you need to install the package for example
-via TER or Composer (via Packagist).
+version 13. On former TYPO3 versions you need to install this package either
+in the Extension Manager or by using Composer (via Packagist).
 
 Go explore!