Please have a look in the argonregister.py to the constants “ADDR_ARGONONREG_” (line 16 - 23). This is the only source of thruth I currently know. 0x80 = ADDR_ARGONONEREG_DUTYCYCLE. I had to look at the different argon1 scripts to understand the new behavior.
This is the register for PWM value 0 - 100. Older firmware versions used the address 0x1a directly. Now the new firmware accept registers at this address and ignores the old fan control commands.
for example fan always on (100% dutycycle) at CLI: i2cset -y 1 0x1a 0x80 0x64
address: 0x1a
register: 0x80
value: 0x64
There is also a new register 0x86 ADDR_ARGONONEREG_CTRL for the shutdown control. In contrast to the fan control, the old command is apparently still supported here.
If not, use bus.write_byte_data(address,0x86,1) instead of bus.write_byte(address,0xFF)
https://www.waveshare.com/wiki/Raspberry_Pi_Tutorial_Series:_I2C
Beware: Please be careful with the i2cdump command, because it leaves the MCU at Argon One V2 case in undefined state (could be a maintenance mode or it may hang). You must power cut the case, before it reacts normal again.