ANSWER: I was told by a Razer customer support representative that my video card is not on the list of approved chipsets. Only "RTX 3080" and "RTX 3080 TI" are on the list of approved chipsets. "RTX 3080 FTW3 ULTRA" is not on the list. Here is the link I was given to the compatible GPUs for the Razer Core X Chroma: 
h ttps://mysupport.razer.com/app/answers/detail/a_id/1727/kw/List%20of%20compatible%20graphic%20chipsets%20with%20Razer%20Core%20X%20and%20Razer%20Core%20X%20Chroma
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Hello,
I just received a brand new EVGA GeForce RTX 3080 FT3 ULTRA (12G-P5-4877-KL). I have it installed in a Razer Core X Chroma (eGPU) and connected to my laptop via Thunderbolt 3 connector, but any time the laptop is turned off or set to sleep, all 3 of the fans on the card kick into maximum speed and don't turn off (it is very loud). This did not happen with my GeForce 1080 card so I am wondering how I can fix this (beyond the solution of “just turn off the eGPU or unplug it every time” because I am bound to forget and it's extremely annoying when I do. I have to run back to the computer, assuming I'm still in the room to hear it, and unplug the cable before it disturbs everyone in the room).
 
I noted a number other people having the same problem, so I am not the only one:

• h ttps://www.reddit.com/r/eGPU/comments/muesq4/gpu_max_fan_speed_while_laptop_is_off_evga_ftw3/
  
• h ttps://insider.razer.com/index.php?threads/gpu-max-fan-speed-while-laptop-is-off-evga-ftw3-ultra-3080.73388/
  
• h ttps://forums.evga.com/EVGA-30-Series-Cards-in-eGPU-GPU-fans-at-max-speen-when-connected-laptop-is-asleep-or-off-m3476270.aspx  
  
• h ttps://egpu.io/forums/pc-setup/egpu-max-gpu-fan-problem-when-laptop-is-sleep-or-powered-off/ (this guy claims to have fixed the issue, but I couldn't replicate his solution as the option to do what he says is not present on my system. But maybe his advice will offer a clue as to what is going on.)
  

 
I’m looking for a bios fix, software fix, drivers, thunderbolt configuration, etc.
 
Is this issue caused due to being a LHR graphic card?
 
By the way, unplugging the thunderbolt cable immediately stops the fans from running at full speed.
 
My setup:

• GIGABYTE AERO 15 OLED YD laptop
• EVGA GeForce RTX 3080 FT3 ULTRA (12G-P5-4877-KL)
• Razer Core X Chroma eGPU

The setup runs games beautifully, Windows runs fine and has no other issue besides this fan issue when powered down (but this is a big issue to me).
 
I seriously appreciate any and all help anyone can provide because I’ve spent hours searching forums for an answer and haven’t found one that has resulted in a fix.

Thank you for your reply. 
 
Given what you said, I have one question: If this happens with some video cards like my 3080, how come it does happen with others? For example, before my 3080 I used a GeForce 1080 in the same enclosure and it did not have this issue with spinning up the fans when the laptop power was off or went into sleep mode. It worked perfectly. So what is the differentiating factor between video cards?
 
I really appreciate the thoroughness of your information.

ANSWER: I was told by a Razer customer support representative that my video card is not on the list of approved chipsets. Only "RTX 3080" and "RTX 3080 TI" are on the list of approved chipsets. "RTX 3080 FTW3 ULTRA" is not on the list. Here is the link I was given to the compatible GPUs for the Razer Core X Chroma: 
 
h ttps://mysupport.razer.com/app/answers/detail/a_id/1727/kw/List%20of%20compatible%20graphic%20chipsets%20with%20Razer%20Core%20X%20and%20Razer%20Core%20X%20Chroma