It's funny: I now use my eink device (Moaan) almost exclusively for music, because there's no streaming so I have to curate my playlist.
For the light theme, try poweramp or the likes that support themes.
> I would never think of daily driving it as a phone if it had a modem
I would never had purchased it if it had a modem. I like to disconnect, I don't want to be tempted by apps.
> And of course, it's running an obsolete version of Android and is continuously phoning home to China, so you probably don't want any important data on it.
I prefer the Mooan because I do not want the google play store on my devices: I can still install apps from F-Droid.
e-ink phone sized devices are excellent for a minimalistic experience: without color or a modem, you are less tempted to use apps.
I also do not want a camera: I prefer the smoother back both to put a credit card holder there, and have no temptation to take a picture.