I followed the instructions and it worked -- who would've thought ;-) Thank you!
I was having sporadic Wi-Fi issues on the previous version, and as far as I can see, the binary blobs for AC3100 were not updated in 384.19.
Tried upgrading through the WebUI's "Manual firmware upload" button, but getting "Invalid Firmware Upload".
Tried rebooting the router and different browsers. Checked the hash of file just in case. Nothing in the syslog.
What would be the best way of diagnosing it?
Is there a different log for...