Dell Latitude 5520 Blackscreen and no keyboard Bios Update 1.44.1

Hello Community,

Unfortunately, after updating my Dell 5520 BIOS to the latest version (1.44.1), the display, keyboard, and touchpad no longer works. When booting, the Dell logo appears shortly on the screen, then it goes black. After connecting a monitor and an external keyboard/mouse via USB-C, I was able to access Windows and the BIOS. I tried installing an older BIOS version (I had previously enabled the "Downgrade Allowed" setting in the BIOS), but unfortunately, the downgrade failed or was not accepted. How can I fix this?

Many thanks and best regards

Marc

Specs attached in Picture: <Private data removed from public view DELL-Admin>