Latest version of Big Sur 11.3.1 gives black screen upon boot
@bootz, It's likely due to a firmware change that came with the macOS update. You'd need an EFI boot loader to keep the iGPU activated when there's an eGPU connected. My recommendation is to use automate-eGPU EFI.
@itsage, Thank you for the suggestion. I did setup the new boot loader, however it wasn't necessary. Apparently putting the eGPU in timeout overnight (unplugged TB and power supply) was enough.
So we are back to normal!