Thanks for the suggestions! I took your advice and commented out the Vega M
device IDs located here: /drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c

These are the lines of code that I commented out.
/* VEGAM */
{0x1002, 0x694C, PCI_ANY_ID, PCI_ANY_ID, 0, 0, CHIP_VEGAM},
{0x1002, 0x694E, PCI_ANY_ID, PCI_ANY_ID, 0, 0, CHIP_VEGAM},

This did indeed cause my Vega M to not be initialized, *but* the problem I'm
having with the eGPU remains. So it appears you were correct and my hunch that
the Vega M is interfering with the eGPU initialization was incorrect.  I'm back
to square one...

I uploaded a new dmesg log for this kernel, perhaps with the Vega M out of the
equation you might see something new?

Thanks!
Rob