Sorry that Lightroom Classic CC side panels and navigator are appearing black.
Are you using a Windows or Mac computer? If on a Mac, please take a look at this article Lightroom UI panels appearing black on macOS and let us know if that helps.
I am using an iMac with OS 10.11.6 . The fix in the link you provided did work on returning the LR side panels and navigator from the black border.
The LR Classic CC version I am using is the most current 7.3.1. The solution suggests updating to LR version 6.10 or later. The solution asks for input with updating the latest LR software only. Please forward my response if needed.
The article also suggests updating to Mac OS Sierra 10.12.4 or later. I have not updated my Mac OS to maintain compatibility with my older laptop which can not install any OS past 10.11.6.
I am assuming that the OS update will be the only option to eliminate this issue completely.
Thanks for the update. Glad to know it helped.