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.
If your gray images in Develop look like those posted in that thread, then try the solution that worked for them: First, set the option Preferences > Performance > Use Graphics Processor to Off. Then update your graphics driver by going directly to the manufacturer's web site, as described here: