Looking at my Moto E6+ on Android 9, it doesn't have the Lens app in the app drawer, in Settings - (All) Apps; and when I search the Play Store app it only offers me alternatives to "Google Lens app".
Still, I can use Lens on it just fine via the icon in the Google Search bar (widgets), as others mentioned.
I can't see Lens on the camera app itself atm, but Google may bring it up if it saw a code.
So Android 9 maybe doesn't like the Lens app but it's part of Google if you bring yourself to install the Search bar, perhaps on another Home screen.