According to this article,
https://smartphones.gadgethacks.com/news/top-4-phones-for-music-lovers-audiophiles-0175956/
the ZTE Axon does not use it's DAC/amp unless you are using the built in music player, it will not use it when using streaming service such as Spotify. Too bad, I would like to find a phone that leaned more towards the bright end rather than warm, but I use Spotify premium a lot, so whatever I get must support that.
I may be exaggerating my preference, but it is important to me to have vocals out in front, with much detail,especially in treble. It seems many of the phones, at least the phones available in USA, lean towards the "warm" side, which scares me off.
Many thanks for your efforts putting this together, much appreciated!