WebDriverManager is a library allows for discovery and download of the correct version of Selenium browser drivers (e.g. ChromeDriver, GeckoDriver for Firefox).
Recent versions of Selenium include a replacement for WebDriverManager called SeleniumManager, which will download and configure browser drivers with no configuration needed.
Serenity framework (among other things) manages setup for Selenium WebDriver. Does Serenity use WebDriverManager or are recent versions of Serenity using SeleniumManager?