Not really an answer to your question, but I recommend using Pipewire with Pulseaudio emulation. That might even work out-of-the-box. See Headphone volume resets itself to 100% - #2 by hmenke for a configuration example.
Not really an answer to your question, but I recommend using Pipewire with Pulseaudio emulation. That might even work out-of-the-box. See Headphone volume resets itself to 100% - #2 by hmenke for a configuration example.