Hello all, I got a Pixel 6a around a year ago at the same as my son and we downloaded Graphene OS together. Suddenly in September, my device failed to boot on morning displaying a red screen saying the device was corrupted similar to this.
Proceeding onward it would display this.
Continuing it would go through the google and graphene boot screens before returning to the charging screen and then the red boot screen again.

After reading a few posts I did the following. I plugged my phome into my computer (with a good USB cable, prefreably the one you installed GOS with) and booted the phone (through the warining screens) until it got to the battery charging screen (where the phone is powered off), then I held Power + Volume Down to get to the bootloader, then scrolled with the volume buttons to Recovery mode, selecting it with the power button.
The phone then went through the red and yellow warning boot screens (I clikced through them with the power button) and then displayed the green Android lying on its back being repaired, with the text "No command". From there I clicked Power + Volume Up to get to the recovery menu.

Then I followed the steps listed on https://grapheneos.org/usage#updates-sideloading to sideload via ADB. This required the installation of the adb command with Android SKD Tools with NexusTools. Read this to understand what you're doing because it can be risky to install software via powershell.

Installing via the Nexus tools instructions will leave the tools in your C:\Users[USERNAME]\AppData\Roaming\NexusTools folder and if you are using Windows powershell you will want to navigate to that directory using the cd command:
cd AppData\Roaming\NexusTools
And then you can verify instalation and function of adb tool with
C:\Users\[USERNAME]\AppData\Roaming\NexusTools> .\adb devices
where the .\ is necessary because we recieved the following suggestion from powershell
Suggestion [3,General]: The command adb was not found, but does exist in the current location. Windows PowerShell does not load commands from the current location by default. If you trust this command, instead type: ".\adb". See "get-help about_Command_Precedence" for more details.
Then you must download the latest stable OTA release of GrapheneOS for your device found here.
put the zip file in your NexusTools directory (AKA folder).
Select "Apply update from ADB" in the recovery menu. My computer then detected my phone and made a windows ping sound and indicating I could run the following to sideload the latest release:
.\adb sideload bluejay-ota_update-2024010400.zip
with the zip file you downloaded subsitiuted in.
Installing a non OTA zip gave us the following errors:
ERROR: recovery: footer is wrong
Update Package verification took 0.8 s (result 1) ERROR: recovery: Signature verification failed
ERROR: recovery: error: 21
ERROR: recovery: footer is wrong Install fron ADB completed with status 2. Installation aborted

Using the OTA update gives the following message:
Update Package verification took 58.2 s and was succesfull (result 0). Installing update... Step 1/2 Error applying update: 7 (ErrorCode: :kInstallDeviceOpenError) ERROR: recovery: Error in /sideload/package.zip (status 1) Install from ADB completed with status 1. Installation aborted.
However, after this aborted upload, I selected the Reboot option in the recovery menu using the volume buttons and the and the device rebooted in safe mode (grayscale)! It is worth noting there was no sim card installed.
I then restarted the device, and the same corruption error came back. I returned to recovery mode as explained in the beginning, and instead of switching to "Apply update from ADB" I selected to just reboot and it booted normally. I then installed the most recent update from within GOS by connecting to wifi. After reboot the phone appears to work normally. Tremendous!

Thanks to the following threads I was able to figure this all out (in order I read them, the second to last link being the most useful for getting to the finish):
Unable to boot into graphene after phone running out of battery
Pixel 5 Device Corrupted Issue
Recover data from "Your device is corrupt. It can't be trusted"
Corrupted device, locked bootloader
“your device is corrupted and cannot be trusted“ - can't start
Here are the boot screens for verifying your issues