I wanted to enable Secure Boot to check if my PC Is compatible with Windows 11, and in order to do that, the UEFI firmware asked me to choose a Protocol/Publisher/Platform key (I don't remember exactly). I choose the default one [I think it was 808 pk], then disabled CSM Support, and now it doesn't boot, with the display remaining black and the keyboard LEDs flashing on and off.

• I tried everything I saw on the internet:
  • reseated CPU, RAM, and GPU
  • disconnected hard drive and connected an older one [10+ years old]
  • tried another GPU [10+ years old]
  • reset UEFI firmware with the jumper and unplugged CMOS battery overnight
    
    
• Specs:
  • MB: Gigabyte H410m s2h
  • CPU: i3-10100f
  • GPU: GTX 1650
  • RAM: 1x 8GB DDR4 2666mhz (HiperX Fury CL16)
  • PSU: Elementium Silentium E2 550w 80 Plus
  • HDD: Western Digital Blue 500GB, 7200rpm

How do I troubleshoot this?

I wanted to enable Secure Boot to check if my PC Is compatible with Windows 11, and in order to do that, the UEFI firmware asked me to choose a Protocol/Publisher/Platform key (I don't remember exactly). I choose the default one (I think 808 pk), then disabled CSM Support, and now it doesn't boot, with the display remaining black and the keyboard LEDs flashing on and off.

• I tried everything I saw on the internet:
  • reseated CPU, RAM, and GPU
  • disconnected hard drive and connected an older one [10+ years old]
  • tried another GPU [10+ years old]
  • reset UEFI firmware with the jumper and unplugged CMOS battery overnight
    
    
• Specs:
  • MB: Gigabyte H410m s2h
  • CPU: i3-10100f
  • GPU: GTX 1650
  • RAM: 1x 8GB DDR4 2666mhz (HiperX Fury CL16)
  • PSU: Elementium Silentium E2 550w 80 Plus
  • HDD: Western Digital Blue 500GB, 7200rpm

How do I troubleshoot this?

I wanted to turn on the Secure Boot so I can check if my PC Is compatibile with Windows 11. In order to do that, the BIOS asked me to choose a "Protocol/Publisher/Platform" key? I don't remember exactly. I choose the default one (808 pk I think it was), and then to disable CSM Support. Now it doesn't boot! The display is black and the keyboard leds flash on and off.
I tried everything I saw on the internet. I reseated the CPU, the RAM, the GPU, I disconnected the the drive, I connected an (older tbh, 10+ years) drive, I used another (again 10+ years old) GPU, I reseted the BIOS with the jumper, I plugged out the CMOS battery, I left away over night. Specs:

• CPU: i3-10100f
• GPU: GTX 1650
• PSU: Elementium Silentium E2 550w 80 Plus
• Motherboard: Gigabyte H410m s2h
• Memory: 1x 8GB DDR4 2666mhz (HiperX Fury CL16)
• Storage: Western Digital Blue 500GB, 7200rpm

I wanted to enable Secure Boot to check if my PC Is compatible with Windows 11, and in order to do that, the UEFI firmware asked me to choose a Protocol/Publisher/Platform key (I don't remember exactly). I choose the default one [I think it was 808 pk], then disabled CSM Support, and now it doesn't boot, with the display remaining black and the keyboard LEDs flashing on and off.

• I tried everything I saw on the internet:
  • reseated CPU, RAM, and GPU
  • disconnected hard drive and connected an older one [10+ years old]
  • tried another GPU [10+ years old]
  • reset UEFI firmware with the jumper and unplugged CMOS battery overnight
    
    
• Specs:
  • MB: Gigabyte H410m s2h
  • CPU: i3-10100f
  • GPU: GTX 1650
  • RAM: 1x 8GB DDR4 2666mhz (HiperX Fury CL16)
  • PSU: Elementium Silentium E2 550w 80 Plus
  • HDD: Western Digital Blue 500GB, 7200rpm

How do I troubleshoot this?