Where are really the log files to debug when a Windows 10 update fails?

Question

I am struggling with Win 10 update:

Feature update to Windows 10, version 1809 x64 2020-03B - Error 0x80070490

Google is swamped with useless articles about random peoples' experiences, but no actual or systematic solutions, and I've already done the usual solutions [DSIM, Sfc]:

• According to my research, 0x80070490 relates to a driver problem, but in Device Manager everything is okay and all devices work as expected (Windows must somewhere place more information than this stupid code)
• Supposedly there should be log files within C:\$WINDOWS.~BT\Sources\Rollback, but Rollback does not exist; similarly, there are no (current) files in C:\Windows\Panther\, or useful info in the Event log

Where does the update actually put the log files?

Answer 1

So, where does the update actually put the log files?

If an update fails to install, the reason for the failure will be contained within %systemroot%\Logs\CBS, and if Windows Update itself has an error, it will be logged within Event Tracing for Windows (.etl) files; a human-readable text file can be generated via PowerShell command: Get-WindowsUpdateLog

Source: Windows Update log files

Supposedly there should be log files in c:\$WINDOWS.~BT\Sources\Rollback but Rollback does not even exist. Similarly, no (current) files in c:\Windows\Panther. No useful info in the Event log.

Based on my experience this log only applies to problems upgrading to another version of Windows.