default or selected kernelversion does not have config value CONFIG_ZX_SPDIF.
Result is shown for kernelversion 6.9.9

ZTE ZX SPDIF Driver Support

modulename: zx-spdif.ko

configname: CONFIG_ZX_SPDIF

Linux Kernel Configuration
└─>Device Drivers
└─>Sound card support
└─>Advanced Linux Sound Architecture
└─>ALSA for SoC audio support
└─>ZTE ZX SPDIF Driver Support
In linux kernel since version 4.1 (release Date: 2015-06-21)  
Say Y or M if you want to add support for codecs attached to the
ZTE ZX SPDIF interface

source code:
sound/soc//zte/zx-spdif.c