MEB,
Thanks for sparking my memory. I forgot that I had originally pointed to a different folder where my Nik Plugins (not the standalones) are living. I'll detail to help others who might have the same issue.
During the installation of the Nik Plugins, I noted that the installer recognized I had a version of Photoshop.
Then I remembered, I originally had Affinity Photo look at the plugins folder for Photoshop Elements:
I told Affinity Photo to look there...
Restarted Affinity Photo, and voilà:
Nik Plugins working again!
It appears the installer was putting the plugin files in the Photoshop directory, and the standalones in the "/Applications/Nik Collection" directory. Maybe it would be different if I had chosen a different directory name. In error I assumed I should tell the Nik Installer to install the plugins into the "/Applications/Nik Collection" directory. Mea culpa.
Again, thanks for jogging my memory. I may not be as sharp as I once was, but I'm as sharp once as I ever was.
Jim