Spoke too soon. The problem persists. I see Daniel McDonald encountered a similar problem with the 2022.2 build that was not resolved for that situation. Seems like a compilation quirk on my hardware (standard 2011ish Dell box).
qiime --help
QIIME is caching your current deployment for improved performance. This may take a few moments and should only happen once per deployment.
[1] 3815128 illegal hardware instruction qiime --help
I have uninstalled unifrac unifrac-binaries using conda and conda also uninstalls q2-diversity plugins. Reinstalling unifrac and unifrac-binaries does NOT cause the problem - only trying to add back the q2-diversity plugins causes this issue. If other architectures do not see this, I will just use 2022.2 until a newer 2023 release appears (and perhaps the gods will smile on my architecture again). This is probably a black hole not worth pursuing of little-ole me - the older version seems to work just fine. Or maybe I can spring for a new box to run it on! 10 years is a long time to be using the same old silicon.