Problems syncing iPhone SE after the latest iTunes update while still on High Sierra
So I'm an old-school fella who prefers copying files from my decade old mp3 collection to my iPhone. Since I'm working with a lot of A/V production software on High Sierra which aren't anymore supported in the newer versions of the OS, I'm at version 10.13.6 and there's zero possibility for me to upgrade to either Mojave or Catalina.
However, I foolishly upgraded to the latest iTunes, which currently doesn't allow me to browse the content of my iPhone, or to add new files. The little icon representing my phone when it's plugged in - gone. Apparently in Catalina now Finder should be used to do those, but my Finder doesn't show my iPhone (connected or not), which I connect through its USB cable as per usual. I saw screenshots that it should appear under devices, on my OS it doesn't.
Alternatively the Apple website directs me towards using Apple Music, which I can't find either in the Apple Store, nor anywhere else as an accessible download, as I suspect it's not compatible with High Sierra and it's only a part of the Catalina package.
What now? How can I still manage the contents of my iPhone, which was also upgraded to version 13.1.2 (the latest one I'm aware of). Seems like I've been either forgotten or completely left behind.
iPhone SE