I have noticed several post concerning inline exhaust fans. Many complained about cost, noise and the need to convert 6" to 4".
Today I took delivery of and installed a new fan that I purchased on Amazon. The price is fantastic, the noise is about 30db and it is 4 inch. I’m getting no smoke in the house and its quite. Best of all it was inexpensive. Below is a link
VIVOSUN 4 Inch 195 CFM Inline Duct Ventilation Fan Vent Blower