kernel_task eating 1000% of my CPU regardless of the CPU being at 56-58 degrees

Solution 1:

I finally fixed it!

After trying 3 different display port cables and 2 hdmi cables, I decided to buy another one from Amazon (it's the highest quality cable I could find. The other ones were very high quality too but apparently not enough)

The cable I bought is made by CABLEDECONN and it's a thunderbolt 3 to DisplayPort cable. It should be available on amazon for both europe and US.

In order to fix the issue though I also had to lower my refresh rate from 144hz to 120hz (this change made no difference with old cables). As soon as I did that, the GPU power usage dropped from 18W to 6W and now my mac idles at 56-57 degrees while in clamshell mode but with fans running at around 2000 rpm (compared to the previous 5000+ rpm). If I also use my macbook's monitor, the GPU power usage ramps back up to 18W but temperatures remain under control and fans run at ~3600-4000 rpm.