Change production key in eas.json to this

"production": {
    "android": {
       "buildType": "apk"
    }
}

So now your eas.json like this

{
  "cli": {
    "version": ">= 0.52.0"
  },
  "build": {
    "development": {
      "developmentClient": true,
      "distribution": "internal"
    },
    "preview": {
      "distribution": "internal"
    },
    "production": {
      "android": {
        "buildType": "apk"
      }
    }
  },
  "submit": {
    "production": {}
  }
}

To build into .apk file, you can build using production profile. The command like this eas build --profile production --platform android