ADtune

ADtune applies a parametric-EQ correction to all system audio using
PipeWire, before it reaches whatever you're listening on: headphones,
speakers, a USB DAC. It ships with a catalog of thousands of measured
headphone corrections to start from, and you can build your own curve for
any device, with a live frequency-response graph and tone controls.

Native PipeWire access requires connecting the pipewire interface once:

 sudo snap connect adtune:pipewire