@Mountain Pond, Thanks for posting in Q&A.
Based on the symptoms you are describing, if an application is listed with the status "Not Installed" in Intune, it means that Intune consider the application is not currently installed on the device. In this case, it is not possible to delete an application that is not installed. Please note that you can only uninstall apps that are deployed through the mobile device management (MDM) channel. You cannot uninstall apps that were installed externally or from outside the scope of Intune. For your situation, if the apps is not installed via Intune, it can be a by default behavior.
To remove the app, if script can do this, you can write a PowerShell script and deploy via Intune to remove the application.
https://learn.microsoft.com/en-us/mem/intune/apps/intune-management-extension
Hope the above information can help.
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