Yeah, that will have to be the way. I looking into lineageos stock kernel and the paths for smartpack kernel manager do not exist. Probably just run outdated software instead for now.

I think the gain for this app is related to the limiter for audio normalization. What I'm trying to do is increase the loudness itself coming from the system to the output device which cannot be done without root as far as I know. Thanks for the suggestion though.

My question is specifically about the kernel and whether flar2 sound patch and/or kernel option is a requirement for smartpack headphone gain to work or not.

I see what you mean, but I don't need an equalizer. I am trying to increase the volume threshold itself. I used to use mixer_paths.xml for this years ago, but even doing that is getting complicated (magisk overlayfs is needed now I guess?). I prefer the smartpack way though as it can be changed on the fly.