Using iKVM (ASPEED) remote text console and GUI desktop session on workstation with discrete AMD graphics

I have the following setup:

• ASUS Pro WS WRX80E-SAGE SE WIFI mainboard with integrated ASMB9-iKVM (IPMI)
• Dedicated AMD Graphics Card that works out of the box with amdgpu driver
• Ubuntu 21.04 Desktop
• ZFS root pool with encryption installation as setup by the installer. Quite nice and fancy, but Ubuntu standard. I did not change anything here on my own.

What works:

• Selecting the dedicated graphics card as primary graphics card in the firmware setup screen (BIOS) gives me a working desktop.
• I configured the IPMI so I can access it from another machine in my network. I also updated IPMI/BMC and UEFI/BIOS firmwares.

What doesn't work:

• When I open the remote console it says "No Signal". There is no video output on the screen like what you expect from a server or a virtual machine.

  • There is one thing though: I get the password screen to enter my ZFS root pool password on both screens, discrete graphics and iKVM. So this looks like a solid implementation.

  

• When I select the internal ASPEED graphics card as the primary graphics card in the BIOS I get video output during boot and I also get my desktop on the iKVM. The problem is: I have not found a way to switch the desktop to the dedicated graphics card.

What I would like to have (My question):

• Use a desktop on discrete graphics. (No Nvidia involved here. Should perform well like plain Intel or AMD systems with their respective graphics solutions.)
• Access the remote console, perform some troubleshooting commands if necessary before power cycling the machine.

So the VGA output isn't "dead" according to what other posts I have read assume, because I can see that password entry screen on both screens just fine.

What I have implemented so far is this recommendation: https://wiki.raptorcs.com/wiki/Troubleshooting/GPU#Tell_GDM_to_ignore_a_GPU

cat /etc/udev/rules.d/72-gdm-ignore-gpus.rules
TAG-="seat", ENV{ID_FOR_SEAT}=="drm-pci-0000_29_00_0"
TAG-="seat", ENV{ID_FOR_SEAT}=="graphics-pci-0000_29_00_0"`

I had to verify the id with ls /sys/bus/pci/driver/ast/ since lscpi stripped leading zeros here.

Now I need to remember that I can access the text console remotely with CTRL+ALT+F3 which should be saved as a hot key. I can control the mouse on tty2 which is the GUI session while the screen stays black on the remote console.

If anyone has a better solution please do tell me.