The version on Play should work. According to the FAQ on system requirements "Any device that runs Android OS version 4.0.3 or above, with at least 500 MB free space and the Android Spotify Music app (downloaded from the Apps store of Google Play".
Sorry. I missed the arm v6 which they stopped supporting 3 years ago. All I can suggest is to download an old .apk from apkmirror or somewhere similar but you need to be very careful and this isn't something I would normally recommend.