[SOLUTION] Admob and Google Play Services work on Unity 2019.2.0f1 (by @derikdf)

IT WORKS FOR ME.

For Unity 2019.2.0f1
* I have not tested on recent versions.

FOR ADMOB:
1 # Import Asset from "GoogleMobileAds-v3.17.0" version, uncheck "Resolver" folder.
2 # Import Asset "play-services-resolver-1.2.124.0" complete.
3 # Import Version Asset: "GooglePlayGamesPlugin-0.9.64", uncheck the "Resolver" folder.
4 # Run Resolver
5 # I put your ID Ads on AndroidManifest.xml, and save.

Assets > Plugins > Android > GoogleMobileAdsPlugin > AndroidManifest.xml

Exemple ID test:
android:value="ca-app-pub-3940256099942544~3347511713"/>

You will now be able to use it.

Downloads:
https://github.com/googleads/googleads-mobile-unity/releases
https://github.com/playgameservices/play-games-plugin-for-unity/releases
https://github.com/googlesamples/unity-jar-resolver/releases/tag/v1.2.124