Thanks MEB for your comment and link. I shall bookmark it and follow.
RE: follow the nik video tutorial.
I really appreciate the video tutorials. Most all are quite clear and very helpful. However, I watched the Nik tutorial several times and tried installing Nik several times but apparently missed the important detail of where to install "plugins". The example given of installing a plugins folder on the desktop is not helpful because no one, I think, would install it on the desktop. AP seems to create a default "plugins" folder somewhere in the Library (where System or User library I don't recall at the moment). Why not a suggestion or two in the tutorial about where it would make sense to install a plugin folder and what best to name the folder? Also, I think the point needs to be made in the tutorial that there is a distinction between plugin files and application files because most of us think of Nik as plugins. (I've had Nik plugins installed in Aperture for years and love them.)
And the problem with my Nik install may be complicated by my long-standing install of the Nik plugins in Aperture, so I think that would be a topic for another thread about "double installs", but after my confusion settles.
Thanks to all the others who commented.
I'm in transition as to workflow. As a long time Aperture user, I'm used to moving back and forth among Nik and other plugins accessible from within Aperture. However, over the past few years, I've adopted DxO for NEF RAW processing. The Nik collection, as you know, is integrated in DxO's latest version but I find it a little awkward to use there. Nonetheless, I export from DxO and open in AP and continue processing. I love AP. The exception to that workflow is in RAW processing of early ORF files that DxO does not support, and I find AP really helpful there for RAW development and further refinement.
RE: Luminar 2018
Strangely, I had Luminar (pre-2018) working with AP. I don't remember what steps I took, but I think I just indicated the location of the Luminar app in the first "add" box. However, Luminar 2018 is a no-go.
Keep up the good work, Affinity. I look forward to better plugin integration.