Long shot but try starting in safe mode just in case it is a driver problem.
No video on an external monitor as well indicates a motherboard problem. (presumably you remembered to press Fn + F2 to switch the display from the laptop to the external monitor).
The laptop has two graphics adapters i.e. one discrete Nvidia GPU and an Intel iGPU. It would be unusual for both to fail so that’s why it might be a motherboard problem.
With the laptop turned on and hopefully booted into the OS, try shining a torch at an angle close to the laptop screen to see if you can detect any images at all. They will be very faint if they are there, so trying this in a darkened room may help to see them.
If you can detect images then there is a backlight problem, but this is only for the laptop screen and not the external monitor.
What is the laptop’s motherboard’s board number? (printed on motherboard itself). The best way to hopefully find the schematics for the motherboard is to search for (insert motherboard board number) schematic, as these may be required to find out what’s wrong.