eas build producing tar.gz instead of aab when running eas build --platform android

Expo Application Services (EAS)
2

can you share some information about your project and eas.json config?

notice the applicationArtifactPath property under the android key in eas.json:

(string) - Path (or pattern) where EAS Build is going to look for the application archive. EAS Build uses the fast-glob npm package for pattern matching (see their README to learn more about the syntax you can use). The default value is android/app/build/outputs/**/*.{apk,aab} .

if your the gradleCommand that you specify produces both apk and aab at the default path then it will be put into a tarball. you can extract that tarball to access both the apk and aab.