In terms of fan control software for the newer models of Macbook Pros, the options are quite scarce. Right now, the main two are smcFanControl and Macs Fan Control. The former hasn't been updated consistenly in nearly a decade, and the backend code it uses to write to the SMC is extremely deprecated, while the former is a paid app with very little technical support. The goal here is to open source a modern version of these types of software that can be supported for future updates of macOS.
Both smcFanControl and Macs Fan control have a minimum fan speed of 1200rpm. This was fine, for the macs prior to 2017. However, in the T2 chipped current models, the fan often idles at 0 until the laptop hits 40C. This is an issue because running the fans at 1200 when they don't need to be on will add unnecessary strain to the fan bearings.
For now, only the smc.c has been developed, thanks to smcFanControl and especially this guy, who just provided the first working version in a while. Navigate to the downloaded folder and run the following:
make
# To get the list of fan keys (will vary by model)
sudo ./smc -l | grep F.Tg
# Set the fans in force mode to control speed
# Replace the keys with the keys found above
sudo ./smc -k F0Md -w 01
sudo ./smc -k F1Md -w 01
# Set the fan speed to 3000 rpm
sudo ./smc -k F0Tg -p 3000
sudo ./smc -k F1Tg -p 3000
# To stop, return to auto mode
sudo ./smc -k F0Md -w 00
sudo ./smc -k F1Md -w 00