Wow, finally zapping via Primal (or anywhere on Nostr) via NWC worked for me. The last days I thought I had distributed a dozen zaps or so. I still don't know what the underlying issue was. A combination of creating a new NWC connection, deleting the old one, and opening Primal in a new tab finally did the trick.

I don't know how I should feel about that. My feelings are quite mixed. My general user experience with Nostr has been one of much confusion and frustration. On the other hand, I feel some elation about finally having mastered the basics.