(In reply to Robert Strube from comment #34)
> Created attachment 143044 [details]
> dmesg log amdgpu.dpm=0 with 580 as eGPU
> 
> Another user is reporting a similar problem with a different Dell laptop
> (the XPS 9370).  He provided two dmesg log files.  This one has amdgpu=0.

It would appear that this user is not experiencing the same issue as you.  In
your case the driver fails to even post the GPU.  That happens long before dpm
is initialized.  The other user can try adding amdgpu.ppfeaturemask=0xfffd3ffb
to disable pcie power management to see if his issue is related to comment 29.