How do I tell what Patches a customer has installed

If this is Windows then you could look in Control Panel->Programs and Features under Installed Updates and the PU version will show as being installed.

Use PowerShell as often these updates are no longer visible depending the operating system:

function Get-MicroFocusInstallations {
    $uninstallKey = "HKLM:\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Uninstall"
    $uninstallKeyWow64 = "HKLM:\\SOFTWARE\\Wow6432Node\\Microsoft\\Windows\\CurrentVersion\\Uninstall"

    $microFocusInstallations = @()

    # Check 64-bit and 32-bit registry keys for Micro Focus installations
    if (Test-Path $uninstallKeyWow64) {
        $microFocusInstallations += Get-ChildItem $uninstallKeyWow64 | Get-ItemProperty | Where-Object { $_.DisplayName -like "*Micro Focus*" }
    }
    if (Test-Path $uninstallKey) {
        $microFocusInstallations += Get-ChildItem $uninstallKey | Get-ItemProperty | Where-Object { $_.DisplayName -like "*Micro Focus*" }
    }

    return $microFocusInstallations
}

# Get Micro Focus installations
$microFocusInstallations = Get-MicroFocusInstallations

# Display the results
if ($microFocusInstallations.Count -gt 0) {
    Write-Host "Micro Focus installations found:"
    foreach ($installation in $microFocusInstallations) {
        Write-Host ("Name: {0}, Version: {1}, Publisher: {2}" -f $installation.DisplayName, $installation.DisplayVersion, $installation.Publisher)
    }
}
else {
    Write-Host "No Micro Focus installations found on this system."
}