Every folder says "No Photos in Selected Folder" (internal hard drive)

Your screenshot shows an inconsistency -- Library filters are off, the selected folder contains many photos, but none are showing in Grid view.  LR can sometimes write inconsistent preferences and cache files that cause such screwy behavior. Try beating LR over the head:

1. In the Library Filter bar, click the preset dropdown menu and do Restore Default Presets. (That won't delete any custom presets you've saved).

2. Ensure the menu item File > Library Filters > Enable Filters is unchecked.

3. Restart LR.

4. Try deleting the Helper.lrdata folder:

a) Do Catalog Settings > General > Show to open Finder / File Explorer on the current catalog folder.
b) Exit LR.
c) In that folder, delete the folder "<catalog> Helper.lrdata".
d) Restart LR, and it will rebuild the folder.

The Helper.lrdata folder caches information about metadata, keywords, folders, collections, and other things to speed the performance of LR and it can sometimes get corrupted. In recent versions, LR has used it more heavily to improve the speed of displaying metadata, and there have been a fair number of bugs with it.

5. Try resetting LR's preferences:
https://www.lightroomqueen.com/articles-page/how-do-i-reset-lightrooms-preferences/

LR sometimes soils its preferences file, and resetting it can fix all sorts of wonky behavior. That article explains how to restore the old preferences if resetting doesn't help.