S2721QS, goes blank

I use a Dell S2721QS (from Sept. 2021, purchased Dec. 2021) which is connected to a Dell Latitude 5289 via HDMI 4K at 30Hz. 

While hooked up to the PC, the monitor initially works perfectly fine for about half an hour and suddenly goes black with no prompt at all. The status LED still works and the panel backlight is on. I cannot call the onscreen menu.

I disconnected all cables (including power) and pressed the power button for 8 seconds. After reconnecting the PC, the monitor works again. Only this time, the problem occurs after only a few minutes later. BID run shows no error.

The PC runs Windows 10 Pro (21H1). The problem occurs on a USB-C to HDMI adapter as well as on the built-in HDMI port. I was able to reproduce the problem with a Xbox Series S via built-in HDMI at 4k 30Hz. Changing the HDMI cable (which worked for quite some time up until last week) did not fix anything.