Great initial troubleshooting! You didn't mention it explicitly (but it is implied), but I'm assuming you've ruled out the cable itself & the input panel on the monitor? (i.e. Display POrt, DVI-D and both HDMI inputs all cause flickering?)
Things to Try: Try all the inputs & verify this issue persists across any input
What's Causing It: (assuing the issue exists across all inputs)
I won't say I'm a well-versed tech person, but I will say capacitors in the power supply backlight-driving circuit are a "common" thing that go bad on monitors & can cause flickering & eventually the backlight goes out (but the LCD screen works fine).
That being said, I wouldn't bet my life on it being a couple of cheap capacitors. Especially since it's an high refresh rate, LED-backlit monitor. It could be a PWM (pulse-width modulation) LED driving circuit or maybe even the entire I/O panel. But if you're someone who takes stuff apart, soldiers & wants to spend a few dollars and gamble that it's just bad capacitors, it's a fairly simple repair. These monitors definitely have some issues as someone else posted another (more text-book-sounding) electronic failure of some type.
