Can the XBOX Companion App be used with an Ethernet connected XBOX on a different network?

They have to be on the same network, sorry but that is the only way they can connect

https://beta.support.xbox.com/help/games-apps/apps-help/how-to-use-game-streaming-in-xbox-console-companion-app

Network connectivity: The Windows 10 PC and the Xbox One console must be on the same home network. Options:

• Wired - Ethernet connection (recommended for both PC and Xbox One console)
  
• Wireless - 802.11 N/AC wireless connection
  

Hello V 1 2 B,

Xbox Console Companion is an app you can install from the Microsoft Store on your Windows 10.

Here you can download the app : https://www.microsoft.com/en-us/p/xbox-console-companion/9wzdncrfjbd8?activetab=pivot:overviewtab

It is recommended that you have both Xbox and PC connected to the network via Ethernet cord.

https://beta.support.xbox.com/help/...-game-streaming-in-xbox-console-companion-app

Is it possible to connect my xbox to my laptop and use my laptop as a tv?

NO, your laptop have an HDMI out, you can workaround this using Xbox Companion App on Windows 10.

If both Xbox One and your laptop use ethernet connection to your network, you can play without any issue.

Hi, I think that worth testing a completely different Wi-Fi network to see if maybe there’s something happening with the current.
Or connect your PC temporarily using an Ethernet connection to see if that improves your latency / ping

In the meantime, please double check what’s your NAT type
For this download and open the Xbox console companion app > settings > network

Are you able to sign in on the Xbox Console Companion App or the Xbox (Beta) app? The Console Companion app has a section under Settings > Network (in the app) that will let you know the network status and if there are any issues connecting to Xbox Live.
Can you let us know what it says in there?