default or selected kernelversion does not have config value CONFIG_SENSORS_HTU21.
Result is shown for kernelversion 6.5.1

Measurement Specialties HTU21D humidity/temperature sensors

modulename: htu21.ko

configname: CONFIG_SENSORS_HTU21

Linux Kernel Configuration
└─>Device Drivers
└─>Hardware Monitoring support
└─>I2C support
└─>Measurement Specialties HTU21D humidity/temperature sensors
In linux kernel since version 3.12 (release Date: 2013-11-03)  
If you say yes here you get support for the Measurement Specialties
HTU21D humidity and temperature sensors.

This driver can also be built as a module. If so, the module
will be called htu21.

source code: