Do you mind sharing sensors readout screenshot from " istat menus " app?
As You can see from my screenshot, my monitor is connected to left Thunderbolt and it is 55 C on idle. Fans are running 2400rpm, which is audible on a silent room.
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I've tried all 4 ports. Charger on and off. LG 4k 650 monitor, with USB-c to hdmi adapter, usb-c to Displaylink adapter, iMac as Thunderbolt monitor. Results are same, always noisy. Contrary, I've tried a 2019 13" Macbook pro, and it is quiet, fans running always at minimum even if connected to a monitor.
I guess I'm gonna return my Macbook 16" and get a new iMac + Macbook Air.