I don't even think I need it as the passive cooling with the Argon One is so good...
Generally yes, you don't really need fan with this case, unless you load your RPi4 CPU to 100% for hours, which is unlikely in case of typical LibreElec box.
My rather heavily loaded (load average: 1.71, 1.22, 1.04) RPi4 running Frigate NVR in docker goes higher than 55C, and I've set fan curve to start at 65C. Such little fan is annoying too, so you'd better keep it off unless really needed.
Code
# argonone-cli --decode
>> DECODEING MEMORY <<
Fan Status OFF Speed 0%
System Temperature 51°
Hysteresis set to 3°
Fan Speeds set to 10% 50% 100%
Fan Temps set to 65° 70° 75°
Fan Mode [ AUTO ]
Fan Speed Override 0%
Target Temperature 0°
Daemon Status : Waiting for request
Maximum Temperature : 55°
Minimum Temperature : 47°
Daemon Warnings : 0
Daemon Errors : 0
Daemon Critical Errors : 0
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But there is another reason to install and configure argoned: it correctly sets up Argon internal microcontroller/PMIC, which allows you to completely power off RPi4 resulting like ~0W power usage, and the turn it on using either infrared remote or power button.