cordova-plugin-googlemaps version 2.6.0 changes installation way.
From this version, you need to specify your API key in config.xml
file.
<widget ...>
...
<preference name="GOOGLE_MAPS_ANDROID_API_KEY" value="(api key)" />
<preference name="GOOGLE_MAPS_IOS_API_KEY" value="(api key)" />
...
</widget>
Installation of this plugin becomes easy. Just install this plugin like other ones.
$> cordova plugin add cordova-plugin-googlemaps
Support cordova version 9.