I’m on macOS 10.13.6 and I have downloaded and installed the KiCad v5 app folder into /Applications, and the kicad folder into /Library/Application Support. Both of those replaced my existing v4 installation.
The app launches and displays my schematics and boards, but the footprint browser will not show any footprints. I go to the Footptint Editor and click Open Footprint Viewer, I get the viewer with with two columns and the viewer area. The first column shows all the footprint libraries, but clicking on one does not show anything in the second column (where all the footprints in that library should be listed).
If they were made with v4 libraries, the application is looking for those libraries.
Many libraries and footprints have been renamed in v5.
Also be sure that the paths of the libraries in your fp-lib-table are pointing to the libraries in your installation.
If you had v4 installed previosly then your personal fp-lib-table will still point to the v4 libs.
There is the possibility that you now have an inconsistent library setup, as the default option was to use the on demand online libs via the github plugin.
If that is the case then your symbol and 3d libs come from the local v5 installation but the footpirnt libs from v4. (You have v4 footprint libs if you have any lib with the prefix Housing in the library table.)
If that is indeed the source of your problem then you have two options. Downgrade symbol and 3d libs to the v4 library or upgrade the footprint lib to v5.
As the v5 footprint libs should already be installed locally upgrading is quite simple. One option is to remove the full fp-lib-table in your users config directory and let kicad replace it with the default one coming with the v5 libs. (This means you will have to manually add your personal libs again after the new fp-lib-table has been created.)
Another option is to use the library manager and remove the v4 libs manually and replace them again manually with the local v5 installation.
In case this helps someone else, I deleted /Applications/Kicad, /Library/Application Support/kicad, and ~/Library/Preferences/kicad, re-installed everything, and now I can create a new project and actually view the built in footprints.
Viewing footprints also seems to work now with existing projects, though obviously my custom footprints are not loaded.