AsRock ROMED8-2D + RTX 3090 black screen on Ubuntu 20.04

Hello there
We are putting together a workstation for AI development using the following hardware

  • AsRock ROMED8-2T
  • EPYC 7352
  • RTX 3090 FE
  • DDR4 128 GB
  • SATA SSD

Ubuntu is able to successfully install with the open source drivers - resolution being limited to 640x480.
OS is then updated to the latest version.
After a reboot, the latest Nvidia drivers are selected and installed. Yet, upon reboot, a black screen is shown with no way to get to the OS.

Using the same 3090 FE on a Intel i7 8700k, the installation goes flawless.

I would greatly appreciate your help with resolving this issue, thank you.

EDIT
Secure Boot is disabled

Update: issue resolved.
We were using PCIe extender cables 3.0 with BIOS settings for PCIe 4.0. Changing the BIOS settings PCIe solved the issues.