Workarounds attempted but failed:
- Pressing manual power button on external monitor affected
- full power-cycle of external monitor
- unplug / plug USB-C between fizz & external monitor

However repeating unplug / plug of USB-C did seem to work.

Filing additional feedback (@login screen) after that

More Feedback logs

https://listnr.corp.google.com/report/85674253078

"2nd external display (LG USB-C) did not come up after auto-update reboot.

feedback for crbug.com/887731 marcheu@ tbroch@"

In modetest the DP monitor (usb-c) is reported as disconnected. So it's a USB-C side issue. Todd, can you take a look?

I'll take a look. Which LG monitor are we talking about?

LG 27UD88

I'm not able to reproduce it.

I tried to emulate the update recorded in https://listnr.corp.google.com/report/85674253078: 
  - AU from 10139.117.0 to 10139.141.0 
  - normal mode
  - Both SPI ROMs are write protected

After reboot, both monitors (LG 27UD88 and HP Z27n) showed pictures normally.

update_engine says:

  Starting firmware updater (//usr/sbin/chromeos-firmwareupdate --mode=autoupdate)
  Command: //usr/sbin/chromeos-firmwareupdate --mode=autoupdate
  Model is sion
  Starting Google_Fizz firmware updater v4 (autoupdate)...
   - Updater package: [RO:Google_Fizz.10139.137.0 RW:Google_Fizz.10139.141.0 / EC:fizz_v1.1.7855-3f7093143]
   - Current system:  [RO:Google_Fizz.10139.117.0 , ACT:Google_Fizz.10139.141.0 / EC:fizz_v1.1.7881-6c20727c6]
   - Write protection: Hardware: ON, Software: Main=ON
   - import root_key from keyset/rootkey.sion: success
  successfully saved new image to: models/fizz_137ro_141rw/bios.bin
  Firmware keys changed to set [sion].
   * invoke: flashrom -p host -r _current/models/fizz_137ro_141rw/bios.bin
  Firmware update available: Google_Fizz.10139.141.0. 
   * invoke: flashrom -p host --fast-verify -w models/fizz_137ro_141rw/bios.bin -i RW_SECTION_B
  On reboot EC update may occur.
  Firmware update (autoupdate) completed.
  Finished after 22 seconds.
  Firmware update completed.
  Starting command: //usr/share/cros/cr50-set-board-id.sh unknown
  Command: //usr/share/cros/cr50-set-board-id.sh unknown
  ERROR: Flag has been set differently.
  ignored: cr50-set-board-id failure (3).
  Finished after 0 seconds.
  Failed Command: //usr/share/cros/cr50-set-board-id.sh unknown - Exit Code 3
  Starting command: //usr/share/cros/cr50-update.sh /
  Command: //usr/share/cros/cr50-update.sh /
  Finished after 11 seconds.
  cr50 setup complete.
  ChromeosChrootPostinst complete
  Syncing filesystem at end of postinst...

I don't know if cr50 update (or its error for setting board-id) is related . I ran cr50-set-board-id.sh and cr50-update.sh as recorded but saw no reproduction.

Another update for me and another occurrence

https://listnr.corp.google.com/report/85697640120

simply rebooting fixed the problem.

This still fails on every AU for me I believe.

https://listnr.corp.google.com/report/85842469582

+abodeti@ to repro this issue.