I installed grapheneos on a Pixel 6 according to the CLI installation guide. I locked the bootloader. Now when it boots it goes to a warning screen, "Your device is loading a different operating system" and shows the boot key hash (which is correct for a Pixel 6).

It flashes the white Google screen briefly, the screen blanks for a few seconds, and it's back to the warning screen. It continues to cycle between the two screens until I use the power and volume buttons to boot the bootloader, where I can power off the phone.

Can anyone tell me what's going on and how to get past this and boot grapheneos?

    redacted I executed flash-all.sh again (for the umpti-umpth time) but this time piped stderr to tee so I could watch the process on the screen and create a log file. It worked this time. Doesn't make sense to me, but there it is. Maybe this will help somebody who encounters the same problem.

    I did the installation from a Ubuntu 22.04 system.