What can I do if there's no sound when my monitor is set to 2560x1440@144Hz through DisplayPort?

Here's how to ensure you get a better experience on XL2566K with its 360Hz refresh rate with DyAc⁺™. 

The first thing is to make sure your PC game supports 360 fps. 

Second, we recommend an Nvidia RTX 30 series, AMD RX 6000 series or newer graphics card connected using the factory original DP1.4 cable that came with the monitor. And, for CPU-intensive titles like CS:GO or VALORANT, make sure your computer works with consistent 360-frames per second output stably, even at the peak of the battle. 

Otherwise, your monitor may not run smoothly at 360Hz and you'll possibly have a worse experience than just playing on a 240Hz monitor.