Hi! to let you know. Yesterday, after installing the Windows 10 update version 2004, Lightroom Classic was horrific to handle, it will work but a slider movement takes 10 seconds, that alone should be immediate, real-time handling, as you all might know 10 secs is an eternity for an app. Every time, every movement, every click was accessing my SSD hard disk like a hungry beast. I did every possible move to improve it but nothing worked.
Then, I decided to roll back and restore the previous Windows 10 installation. Result? back to business. This seems to be related more to Windows 10 Pro version 2004 because I noticed that other applications were slow and behaving differently. Best regards.
When upgrading the OS it's always worth reading through what changes have been implemented. In some cases the changes can have a significant adverse impact on some applications, especially if left at defaults.
I'm not a Windos user. However, reading the release notes for 2004 I notice that one of the feature improvements mentioned is Windows Defender.
If you left it with new default settings it's possible that the realtime checks that it carries out in the background may well have been interfering with the Lightroom catalog and preview, which the application is continually updating.