Johnason

It doesn't support Spotify app installed on your TV.  Try to upload Spotify music to it. You can download them by the AudFun Spotify Music Converter, and transfer them to a USB drive. Spotify Connect need both TV and phone to have the Spotify app, and that's impossible for the old version TV.

If you can use the Spotify web player, how about just download and play Spotify on LG Smart TV. What I use is the AudFun Spotify Music Converter that will convert the music from Spotify to the format that is supported by LG TV.  You then just need to import those Spotify songs to LG TV and you can listen to them without the Internet and app.

Is that the Internet problem? I most time will prefer listen to the music offline, so you can try to download Spotify music to a USB and plug it on the LG TV. That will be easier if you are with AudFun Spotify Music Converter, which can solve all the problems to stream music from Spotify. But if your Amazon Music worked fine on the TV, just use Amazon Music, that's the most efficient one.

Though there is no Spotify app on your TV, you can also listen to Spotify music on it by using another way. Here you can use the AudFun Spotify Music Downloader to download Spotify songs as local files on your computer. Then you can move the local Spotify songs to your TV for playing offline. Also, you can transfer the downloaded Spotify music files to other platforms and devices for enjoying as you want. 

Thanks for sharing. I have a Spotify music converter and I had used it to download Spotify songs to MP3 for use on LG Smart TV. It is the tool from  AudFun, which is great and easy to use. With it, I can enjoy Spotify music anywhere and anytime.