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It may be the error described here: P: Blackouts on secondary display in LR14.1 - Adobe Community - 15037347

What 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/troubleshoot-gpu.html

If it's help see here Troubleshoot GPU issues | Lightroom Classic (adobe.com) and check the different steps.

Make also sure that you have the recent "Studio version" driver for your graphic card are installed. Don't use the "Game Ready" driver.

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 all doesn't help, please provide also a copy of your 'System Info'. This can be get from the LrC Help > System Info menu item. There's a copy button in the System Info dialog. Press this button and paste the info into your next forum post.