Does LineageOS break DSD support? And UAPP doesn't seem to work at all, either. Neutron can play music but not DSD files.

It depends on your model number and current Android version, mine was a US998 model (which is the easiest one to do) with Android 9 so I had to downgrade it to an early version of Android 8 using a patched version of LGUP to unlock bootloader then upgraded to Android 9 again then I can install...

Yeah it does get very loud even with the volume amplifier at -14, good to know it's a Hi-Fi Status problem and not my phone, just wanted a way to be 100% sure that the DAC is active. It does sound amazing with my Mega5EST for sure and hopefully that's because of the DAC.

Hello, I have recently bought a used V30+, rooted it and installed LineageOS 21 (A14) onto it, does it affect sound quality if at all? There's a DAC panel in the settings app and changing the settings in it also changes the audio output (you can also select gain modes in there.) so think the DAC...

I have found Neutron/UAPP to be your best bet