Access UEFI Settings with Discrete Card Only
Solution 1:
Ok, afrer a while I found out the issue.
I'm using an Odyssey G9 monitor and it has the option to "lock" the Refresh Rate. In my case it was set up to 240Hz which made my screen look black as default UEFI interface refresh rate was 60Hz.
I switched the Display Port 1.4 Cable for an old HDMI 2.0 and connected it directly to the RTX Card, which made the monitor lower the Refresh Rate to 60 Hz and boom! I was able to access the UEFI settings!