Modern phones (Pixel 8 included) encrypt their data by default: since factory reset wipes out the encryption key, there is no way to recover the data, so you should be safe.
post
replies:
I know with some phones (lg specifically), a partition that recorded certain telemetry data (all your passwords, location, sms, calls, lol) survived full system resets.
https://xdaforums.com/t/mlt-apk-disable-or-remove-lg-is-watching-you.2187920/page-6
The only absolutely certain way to leave no data would be to flash the firmware and all partitions.
Because you have a pixel, you could flash graphene and then flash back to stock.
Remove any accounts first and reset device so you don't run into frp issues.
replies:
You might be able to overwrite the data partition with this custom recovery
Do sign in again with a random login so it's less likely to connect again with your regular account then factory reset again.
all 7 comments