I own a Dell S2721QS 4K 27" monitor, and I have experienced the infamous "flickering issue" from day 1.

This is my second Dell monitor (I had a replacement for the same problem), and my replacement unit has exactly the same problem.

The only way you can get around it is by getting a refund or a used replacement from Dell from unaffected units (Ultrasharp models aren't affected AFAIK). Getting a replacement of the same model affected by the "flickering issue" will only cause frustration.

Dell never acknowledges the issue, and they always reply to you with the same troubleshooting in loop: factory reset the monitor, unplug it, change the cable, etc. Truth to be told, most Dell monitors are faulty from the factory and this problem has to do with either the firmware or internal electronics. It's a hardware problem.

Don't waste your time buying a new cable, a new hub, changing the color profile or anything like that. You are wasting your time. Get a refund or chargeback if you can.

Most of the time, unplugging the monitor and factory resetting it "solves" the problem because the brightness gets reset to an higher value. Flickering happens on low brightness settings, settings the brightness at the maximum level for a few minutes will solve the issue temporarily.

I will never buy a Dell product ever again. Horrible support, terrible quality. There are much better alternatives out here, which provides high quality monitors for the same price.