In addition to software solutions, how’s your hardware setup?
How far are you from your mic? And where is your fan located relative to you and your mic?
Do you have a dynamic mic or condenser mic? I’m not an expert, but I believe condenser mics tend to pick up more ambient noise from anywhere in the room compared to dynamic mics, which tend to more directional in nature.
In addition to software solutions, how’s your hardware setup?
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You should also look into the polar pattern of the mic you're getting.
You'll probably want a dynamic mic with a cardioid, hypercardioid, supercardioid or subcardioid pattern.