Lightroom Classic: Very slow rendering in Develop module

Currently I am running release 8.3.1 with Camera Raw version 11.3.  But I've been through a number of updates since my original post in March.

"My Lightroom version was up to date as of the time of my post."

Unfortunately, the CC desktop app isn't reliable and often fools people into thinking they're on the "latest", when in fact they're sometimes a year or more out of date.  Can you do Help > System Info and tell us the exact version you're running now?  Thanks.

Sorry for the very late reply. 

Yes I am saying there was a marked improvement in performance when I removed those plugins.  My Lightroom version was up to date as of the time of my post.  I certainly never ran those Plugins, maybe they were running in the background?  I don't know.  I do know this I did not install any of them.  They were installed for me during the Lightroom install process or during an update.  Lightroom is running quite well these days.

David, just to clarify, are you saying you were having performance issues and these went away when you disabled these plug-ins? These particular ones shouldn't be doing anything unless you're actively using them, so that could be a useful tip. If you go to Help menu > System Info, can you please confirm which LR version you're using too?

yes, you are receiving a comment three years later.  But thanks for this tip.  I was unaware of the plugins as I had never installed any myself.  Imagine my shock and horror when I saw that I was running Adobe Stock, Facebook, Flickr, and Nikon Tether.  I don't use any of those.  I don't have a Facebook account. I don't have a Flickr account, and I don't own any Nikon cameras.  Adobe installed these without my knowledge - crippling Lightroom for me.  Ridiculous.

I have the same issues - slow LR. I have a 2nd monitor - sometimes takes 5 seconds for adjustments to show up there. Crazy mouse action (resize crop and then it flips 45 degreess and shrinks to a dot), etc. Resetting LR sometimes helps;

Based on suggestions - i disabled all plugins..and so far so good!

Yep, I used to do something similar.  I had everything in LR referencing a mapped 'network' drive, even though that drive was still internal.  When I wanted to force faster speed using the smart previews, I just selected 'disconnect'.
I finally JUST got around yesterday to converting the references to point directly to the files, given the new option.  But I suppose keeping it that way would have also enforced the smart preview use even when zooming in 1:1.  In which I've been noticing a slowdown when going 1:1 as it reads the real raw file.  ...  Ehh..  I suppose if it gets to be too much, I'll just re-reference them again - now that I know how, using the 'update folder location' of the right-click menu on the folder.

After a full season of tears @ Lightroom CC, I finally resolved the painstakingly slow performance in the Develop module. I copied the RAW files to an external HD - I then created Smart Previews using a Lightroom catalog on a standard internal drive. I then unplugged the external HD containing the originals and found that this totally transformed the performance. I noticed that Adobe have now included the option to "work on smart previews when in develop mode" but the metho9d above works much better.

Just making sure.. But have you tried to turn on the option in Preferences-Performance, to use Smart Previews for editing?  If you haven't, it might help.  Also try disabling the GPU in case the GPU-offloading time is a culprit.

I have found that Lightroom 5.7.1 is much faster in the develop module when using arrow keys to move between photos than Lightroom CC 2015.x   I had signed up with creative cloud and had been complaining for several months about the poor performance of Lightroom in Develop mode. It drove me nuts..sometimes I'd hit the key a few times and then sit there waiting for it to finish moving 3 photos over.  I tried everything, all kinds of suggestions. I put my catalog and cache on an SSD drive and then the photos themselves on another SSD drive...it was still laggy.  
When I ugpraded to a 40 megapixel camera, the performance was so much worse that now I really started to dislike Lightroom.  I started looking at alternatives...
Then I read somewhere how the older version of Lightroom was faster.  So luckily using creative cloud I'm able to install the previous LR version 5.7.1.  Now its not able to read my sony a7RII raw files, but I converted them all to DNG and I'm now able to use both 5.7.1 and LR CC 2015 on the same DNG files.  
The performance difference is blatantly obvious.  
It bothers me that Adobe has this much newer version with so many updates, and yet they seem to have gone backwards.  
So in both cases with 5.7.1 and CC 2015, I have the same drives, same DNG files...only difference is the catalog.  
My computer is a 4 Ghz I7 with 32 gigs DDR3 RAM.  video card has 4 gigs of DDR video memory.
But the fact that 5.7.1 is so much faster tells me that my computer has nothing to do with it...its the software.