This worked for me.
As per
To uninstall [GameBar] open a powershell as administrator and uninstall it with the following command:
Get-AppxPackage Microsoft.XboxGamingOverlay | Remove-AppxPackage
However this left me with a nagging popup upon game start:
you'll need a new app to open this ms-gamingoverlay-link
To resolve this you can also use the powershell to edit the registry like this:
reg add HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\GameDVR /f /t REG_DWORD /v "AppCaptureEnabled" /d 0 reg add HKEY_CURRENT_USER\System\GameConfigStore /f /t REG_DWORD /v "GameDVR_Enabled" /d 0
This disables the game recorder software which seems to still think that the gaming overlay is still present.