I have a Dell XPS13 bought in 2016 in the US.  I removed Windows and installed Ubuntu and it's been working great.  I have the i7/8gb ram/4k touchscreen model.

Today, when I tried to start it, the LCD stayed blank as it booted.  I know it booted because when it reached the login screen, it played the ubuntu login/ready sound -- except the screen was still blank.  The backlight works, as well as the keyboard backlight, but the screen is completely blank.

I rebooted and tried various key combinations until I got to the BIOS and went into Ubuntu's recovery mode and installed all updates and then rebooted again...

And it booted back to the blank screen.  I've tried all the various key combinations, and can no longer even get to the BIOS boot screen, even though it still boots to the ubuntu login screen ( I assume -- screen is still blank ) when I can hear the ubuntu login/ready sound.

I tried the LCD test (PWR + D) and all colors display fine.  I also held down PWR + FN and got a series of very loud beeps, 6-5 beeps separated by a second or so, and then a musical series of beeps that repeated itself.

Now when it boots, I don't see the DELL logo anymore, and really have no indication anything is happening until I hear the login sound.

Any idea what is happening?