I had that at one point too, was really obnoxious. A couple fixes:
Bluetooth, including possibly a Bluetooth-to-phone-jack adapter if you have headphones with a phone jack that you’re happy with.
USB-C audio interface that has better power circuitry than the phone’s DAC. You will need one that can pass through USB PD to charge your phone simultaneously.
Charging circuit could do with more isolation. When I am charging the phone there is noise that comes through to headphone jack.
I had that at one point too, was really obnoxious. A couple fixes:
Bluetooth, including possibly a Bluetooth-to-phone-jack adapter if you have headphones with a phone jack that you’re happy with.
USB-C audio interface that has better power circuitry than the phone’s DAC. You will need one that can pass through USB PD to charge your phone simultaneously.