Microsoft: Yes, you CAN plug a PS4 into the Xbox One, but

If you live outside the United States, you can still use HDMI pass-through to view TV content through Xbox One, but the OneGuide will not show your TV listings. Requirements Buy Xbox Game Pass for Console - Microsoft Store Xbox Game Pass is an Xbox One, Xbox Play Anywhere, and Xbox 360 backwards compatibility game subscription for Xbox One; an active subscription is required to play games. Titles and number of games included may vary over time and by country, and may not be available in all countries. Xbox One X - Passthrough/HDMI In Question : xboxone

Xbox Support loading

This item Pengo 4K HDMI Pass-Through Grabber, USB 3.0 UVC Game Capture Card at 1080p@60, Works with Win10, Mac OSX, Live Stream for PS4 (NO HDCP), Xbox One, Switch [USB-C Connector Bundle] (Aluminum) Plugable USB 3.0 to HDMI Video Graphics Adapter with Audio for Multiple Monitors up to 2560x1440 (Supports Windows 10, 8.1, 7) Microsoft confirms that PS4, Wii U will work with Xbox One

Xbox Series X won’t beat PS5 — but Xbox Game Pass could

The Xbox One’s HDMI Pass-Through Can Put a Console in Your Sep 20, 2013