The adapter required to plug headphones into a smartphone that has eliminated the traditional analog 3.5mm socket. Such devices only have a USB Type-C socket for a wired connection to a charger or external device. The problem is that not all USB-C ports in a phone support analog output. See
analog audio,
mini-phone connector and
USB Type-C.
Not All Adapters Work
USB-C Audio can be analog or digital. Because earbuds have traditionally been passive analog devices (no conversion), the USB-C port must output an analog signal. The only true way to tell is to try it (like most everything in the tech world).