Defunct keyboard after GRUB freeze.

Grub got frozen after pressing ‘E’ to edit menu item and scrolling down using cursor down key.
Shutdown using Power off button was needed. Keyboard is defunct now with exception of Power off button. I can’t even enter BIOS. Mouse is working fine. I don’t see any error / warning message on boot screen messages.

Laptop, Legacy BIOS used.

Is keyboard definitely dead ?

I would find a USB keyboard to plug in and try booting with.

USB keyboard is working fine.

With the USB keyboard, try a BIOS reset, then try to power up without the USB keyboard connected.

After shutdown and unplugging power, keyboard is working again, no need for USB keyboard. The only visible change is that GRUB changed from “window” mode to “fullscreen”. I hope there is no other change of system.