Default volume key control LineageOS So I prefer how my iPhone works in that the volume keys adjust the media volume.  

Samsung has an option for this called "Default volume key control."

Is there a way to do this on a rooted device?

Basically I don't like how there are 2 separate volumes that I have to deal with.  I just want one.  I put my phone on silent when I don't want it to ring so I'm not concerned about the ringtone volume.
Media volume only does exactly this but does require accessibility settings.  Supposedly it doesn't drain your battery but I'm not 100% sure.

There is other options here https://www.xda-developers.com/apps-to-master-your-volume-buttons/
I experimented with a couple apps but ultimately many of them don't for example if your screen is off.