Before we discuss the plugin, we must understand the host. JoiPlay is an Android application available via GitHub or the official JoiPlay Patreon page (not the Google Play Store, due to policy restrictions on emulators). It simulates the critical system libraries that PC games rely on.
Visit the official JoiPlay page (Patreon or GitHub releases). Look for a file named: plugin.unity.release_vX.X.X.apk joiplay unity plugin