Lightroom classic turns dark

Please post your System Information as Lightroom Classic (LrC) reports it. In LrC click on Help, then System Info, then Copy. Paste that information into a reply. Please present all information from first line down to and including Plug-in Info. Info after Plug-in info can be cut as that is just so much dead space to us non-Techs

The first thing that you should try is to switch off the GPU support from the Lightroom preferences and check if that helps to fix the issue. 

Go to Lightroom > Preferences > Performance tab > Uncheck "Use Graphics Processor" > Restart Lightroom. 

https://helpx.adobe.com/lightroom-classic/kb/lightroom-gpu-faq.html#troubleshooting 

https://helpx.adobe.com/lightroom-classic/kb/troubleshoot-gpu.html 

If Lightroom doesn't start correctly the please see "Solution 2" in the document behind the second link. 

Troubleshoot GPU issues | Lightroom Classic (adobe.com) 

Another step is to try to reset the Lightroom preferences. 

https://www.lightroomqueen.com/how-do-i-reset-lightrooms-preferences/ 

It's recommended to backup your preferences before you reset the preferences to the default settings:  

https://helpx.adobe.com/lightroom-classic/kb/preference-file-and-other-file-locations.html 

If this doesn't help we need more informations about your environment. 

Which operating system do you use? 

Which version of Lightroom do you use? 

Please post the exact version and not only phrases as "recent", "latest" and so on.