Well, I didn't wait. Apparently once New Zealand passed midnight on their 05-Oct, the Microsoft servers made the Win11 ISOs available. Against my left-brain caution, I downloaded Win11_English_x64.iso and did an in-place upgrade on my SP6. From clicking the setup.exe file it took a little over 40 minutes to reach a usable Desktop.
I had been using the Insider Preview (Dev) releases, so there's nothing new to see. I had been running the previews in a VM, though, so this is the first time on the "actual" SP6.
If I experience any instability or other weirdness, I will wipe the drive and do a clean install, but so far the in-place upgrade seems stable. Hopefully you will not hear from me about a bricked SP6.