Firmware is out
Still not 100%, I tested this on my Pixel 5 and got stuck at rescue party too...with the stock images.
If it makes you feel any better, those of us who updated to Android 12 already have another update notification, but the OTA hasn't been posted to Google yet, so there's no way to compare the build number.
The solution, if you can call it that, was to avoid the automatic OTA; instead, sideload the OTA via ADB, then enter fastboot without rebooting, and flash /vbmeta and /boot.I don't have the experience with messing with dm-verity so I can't answer for sure (someone else correct me if I'm wrong), but I think it's a one time thing, so long as you don't flash vbmeta again without it? So basically don't use flash-all and flash the images manually, skipping vbmeta.
V0latyle was also saying that the requirement was worked around on the other Pixels anyway so it might not even be required by the next monthly patch.
In fact, re-reading his message again I could probably have got stock to boot again if I re-flashed vbmeta, which just shows my lack of experience with the newer Pixels.
Still not 100%, I tested this on my Pixel 5 and got stuck at rescue party too...with the stock images.
If it makes you feel any better, those of us who updated to Android 12 already have another update notification, but the OTA hasn't been posted to Google yet, so there's no way to compare the build number.