Allowing an Android app to be moved to an SD card by the user (untested)

AndroidManifest.xml

<!-- Need to specify the `installLocation`. Can do this with a config plugin -->
<!-- See `app.json` and `withAndroidManifestAttributes.js` below -->
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myapp"
    android:installLocation="auto">
    ...
</manifest>

app.json

{
  "expo": {
    // ...
    "plugins": [
      [
        "./withAndroidManifestAttributes",
        {
          "android:installLocation": "auto"
        }
      ]
    ]
  }
}

withAndroidManifestAttributes.js

const { withAndroidManifest } = require("@expo/config-plugins");

function addAttributesToApplication(androidManifest, attributes) {
  const { manifest } = androidManifest;

  manifest.$ = { ...manifest.$, ...attributes };

  return androidManifest;
}

module.exports = function withAndroidManifestAttributes(config, attributes) {
  return withAndroidManifest(config, (config) => {
    config.modResults = addAttributesToApplication(
      config.modResults,
      attributes
    );
    return config;
  });
};