A few months ago I was in the process of bringing an old app up to date for Googles 64bit rules and such. It took me a while but I was able to get my old pipeline set up, and building with ADT to 32bit and 64bit.
After some refactoring and other preparations to the game, it is ready to ship again!
Everything is running great from my IDE (FB) - I do a 32 and 64bit build and those compile with no errors. I take them to device (Samsung Galaxy S10) - For some reason, only the 32bit build plays. The 64bit build will start, I see the Harman splash screen and then the app just closes. I snooped around the .apk for the 64bit build and it is in fact 64bit. Back when I started this in October, I was able to playback a 64bit build on my device (I'm pretty sure). Not really sure what may have changed or areas that I could double check.
Here are the lines I used for each build:
adt -package -target apk-captive-runtime -storetype pkcs12 -keystore coolgame_cert_android.p12 -storepass redacted CoolGame_x86 Main-app.xml -extdir Extensions Main.swf ico/. Media/.
adt -package -target apk-captive-runtime -arch armv8 -storetype pkcs12 -keystore coolgame_cert_android.p12 -storepass redacted CoolGame_x64 Main-app.xml -extdir Extensions Main.swf ico/. Media/.