Lightroom Classic can not add existing folders

So inquiry:

What is your exact Lightroom Classic version. The version number. v8.3.1???

What are your exact steps in your attemt to add an existing folder into the Lightroom Classic catalog? Be specific, be wordy, include screenshots.

Note that I deleted a previous comment. Revisiting what I was thinking the following is my thoughts on the YoueTube vide you linked.

In that YouTube video, the author appears to have done something ilogical . What was that about an imoprt of a catalog. He has muddled things up. Bad example.

Just experimented on my MACBook Pro.

Experiment 1. Empty new folder

Outside of LR Classic, created  a new folder. In LR Classic went into Folders panel, clcked on the +. Selected Add Folder, pointed to new folder. Bingo it was added, no Import screen, just a nice empty folder. (and LR stated as such,i.e. no i mages)

Experiment 2. Populated folder

Ok, but what if the folder had images? Outside of LR Classic, created another new folder. This time copied some images into it (outside of LR). Launched LR Classic, Add Folder. Yes, an Import screen came up. Images shown. Import was in ADD mode. Clcked on Import. Worked fine.

As above, in different words.

Do not create a new folder with your operating system file manager. Create the new folder you want to show in LR from inside LR.

True, but I never found that to be a problem. You can create an empty folder from within Lightroom. That folder will be shown in the folder panel, even though it does not contain any images yet.