In case you still need help on this, I have a little “script” that I follow every time I want to upload an app on Google Play (based on the Meteor Mobile guide).
1 - Run
meteor build ../build --server <your_app_url>
This will generate a build folder.
2 - Copy android-release-unsigned.apk from its directory inside the build folder (~/build-output-directory/android/project/build/outputs/apk/) to the root of the folder (~/build-output-directory/android/).
3 - Using the command line, navigate until the root of the build folder and run:
keytool -genkey -alias <your_app_name> -keyalg RSA -keysize 2048 -validity 10000
4 - Next, on the command line run
jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 android-release-unsigned.apk <your_app_name>
5 - Now comes the trickiest part. You have to know where to find the “Android/sdk” folder in your computer. Usually its in Library. So the next thing you’ll do is run the following command:
Library/Android/sdk/build-tools/28.0.3/zipalign 4 <path_to_your_build_folder>/build/android/android-release-unsigned.apk <path_to_your_build_folder>/build/android/<your_app_name>.apk
This will generate a <your_app_name>.apk file that is ready to be uploaded on the Play Console.
6 - Open Google Play Console, create a new app and on “Versions” you will find the place to upload your apk file.