Setupdiag said:
Error: Found system boot failure.
Last Phase: FirstBoot,Start.
BootLogErrorCount: 1
LastErrorEvent: 80
LastErrorCode: 0
The troubleshoot page said:
First boot phase: Boot failures in this phase are relatively rare, and almost exclusively caused by device drivers. Disconnect all peripheral devices except for the mouse, keyboard, and display. Obtain and install updated device drivers, then retry the upgrade.
I previously did the system stripdown and made sure all my drivers are up-to-date. I previously saw that there was a problem with an IBM SSD driver and downloaded the fix for that but it said not applicable to my system.
Then the troubleshooter page said: "If the general troubleshooting techniques described above or the quick fixes detailed below do not resolve your issue, you can attempt to analyze log files and interpret upgrade error codes. You can also Submit Windows
10 upgrade errors using Feedback Hub so that Microsoft can diagnose your issue."
I think I'm there. I'm an experienced PC user but I'm over my head.