Does NepTunes support scrobbling from devices?

Well no, and I don't have plans to implement this kind of functionality. There is a reason why it's so buggy in official Last.fm client – it's super hard to make it. Imagine iTunes, connected to cloud where devices remotely updates library with no support from Apple, which means that it can broke after any iTunes or macOS update. That's why I don't want to touch it. It wouldn't be reliable.