For a GA-Z170N-WIFI (rev. 1.0), just modprobe it87 is enough, you can just load the it87 module without any options. This enables not only fan speed sensors but also voltages and various other temperature sensors
echo it87 > /etc/modules-load.d/gigabyte-sensors-it87.conf
Full sensor output:
~ sensors
iwlwifi_1-virtual-0
Adapter: Virtual device
temp1: +33.0°C
it8628-isa-0a40
Adapter: ISA adapter
in0: 300.00 mV (min = +0.00 V, max = +3.06 V)
in1: 2.03 V (min = +0.00 V, max = +3.06 V)
in2: 2.02 V (min = +0.00 V, max = +3.06 V)
in3: 2.02 V (min = +0.00 V, max = +3.06 V)
in4: 12.00 mV (min = +0.00 V, max = +3.06 V)
in5: 1.07 V (min = +0.00 V, max = +3.06 V)
in6: 1.36 V (min = +0.00 V, max = +3.06 V)
3VSB: 3.38 V (min = +0.00 V, max = +6.12 V)
Vbat: 3.14 V
fan1: 1520 RPM (min = 0 RPM)
fan2: 20454 RPM (min = 0 RPM)
fan3: 0 RPM (min = 0 RPM)
fan4: 0 RPM (min = 0 RPM)
fan5: 0 RPM (min = 0 RPM)
temp1: +37.0°C (low = +127.0°C, high = +127.0°C) sensor = thermistor
temp2: +44.0°C (low = +127.0°C, high = +127.0°C) sensor = thermistor
temp3: +42.0°C (low = +127.0°C, high = +127.0°C) sensor = Intel PECI
temp4: +45.0°C
temp5: +37.0°C
temp6: +32.0°C
intrusion0: ALARM
acpitz-acpi-0
Adapter: ACPI interface
temp1: +27.8°C (crit = +119.0°C)
temp2: +29.8°C (crit = +119.0°C)
coretemp-isa-0000
Adapter: ISA adapter
Package id 0: +43.0°C (high = +74.0°C, crit = +80.0°C)
Core 0: +43.0°C (high = +74.0°C, crit = +80.0°C)
Core 1: +41.0°C (high = +74.0°C, crit = +80.0°C)
Core 2: +42.0°C (high = +74.0°C, crit = +80.0°C)
Core 3: +41.0°C (high = +74.0°C, crit = +80.0°C)
nvme-pci-0b00
Adapter: PCI adapter
Composite: +41.9°C (low = -5.2°C, high = +79.8°C)
(crit = +84.8°C)
fan1 is CPU and fan2 is SYSTEM. Looks like the system incorrectly reports a high RPM number when the fan is receiving some voltage but not enough to spin it up