https://helpx.adobe.com/lightroom/kb...m-gpu-faq.html
(Windows) Navigate to C:\Users\[user name]\AppData\Roaming\Adobe\Lightroom\Preferences\Light room 6 Preferences.agprefs
Open the file Lightroom 6 Preferences.agprefs (Windows)/com.adobe.Lightroom6.plist (macOS) in a text editor.
Change the line useAutoBahn = true to useAutoBahn = false
Save and close the file Lightroom 6 Preferences.agprefs (Windows) / com.adobe.Lightroom6.plist (macOS).
Re-launch Lightroom.