Sorry to leave that out. What's weird is it ran like butter until 11.4. Now, especially on dual screen, the main proofing imagine wont update for minutes. And when I click a simple option like "Auto" Tone, it takes a long time too.
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.