It turns out that at this screen resolution, the Pi 4 emits some RF noise which is exactly in the range of WiFi channel 1. It seems that the Pi 4 is acting as a WiFi jammer on itself.

Raspberry Pi 4 users are trying to get to the bottom of an odd glitch that causes Wi-Fi to stop working when the display output resolution is set to 2,560 x 1,440 or higher. Fortunately, The ...

Alternatively, if you have Raspberry Pi 1, 2, or 3, you can easily connect them to a screen using a standard HDMI to HDMI cable, as they come with a single full-size HDMI port.

The Raspberry Pi 4 is a true next-generation Pi, with dual-screen 4K support, USB 3.0, a new CPU and GPU, and up to 4GB RAM.

The Raspberry Pi 400 is the brains of the operation, while the touch screen LCD provides the display. You’ll also need a keyboard, mouse, and power supply for the Raspberry Pi 400.” ...