My monitor is Dell U2719D.
My refurbished mac is;
2.6 GHz 6-Core Intel Core i7
32 GB 2667 MHz DDR4
AMD Radeon Pro 5300M 4 GB
Intel UHD Graphics 630 1536 MB
It is heart pain to see and hear my new (yes refurbished. but its new for me) mac fan spinning crazy.
With HDMI cable through Baseus usb c hub, draw 18+W by Radeon High Side, regardless of clamshell mode or not.
I tried one another brand of usb c hub also. Still the same issue.
Then I tried SwitchResX method as a few suggested in this thread started from page 75.
But it is not working for me.
Then I started seeing Displayport solutions in this thread.
So I bought a Displayport to usb c cable.
Now it draw only 5+W by Radeon when using clamshell mode.
Once laptop monitor open, it immediately raise to 18+W.
After close lid again, waited like 10 minutes, but it is not dropping back to 5+W.
So I restarted the mac in clamshell mode and it drop back to 5+W.
After play around with Displays setting from System Preferences, 18+W issue come back.
Then found out that SwitchResX also plays a role to make this remedy works.
This is the setting that works;
View attachment 929011
View attachment 929014
And for extra touch, I disabled the cpu turbo boost also.
With this issue, mac book pro is not so "pro" after all.
Now I have to use in clamshell mode until this issue is resolved.
Finger cross and hope this is just software bug and could be able to resolve in near future.
I posted a feedback to apple also. Hope apple will listen the voices and make the software fix faster, if it is fixable.