Can you elaborate? “If you try installing a version of /e/OS based on a security patch that is older than the one on your device, you will brick your device.”
The proposed downgrade will have an older security patch level in this case, and Android rollback protection doesn’t care about the way you try to install an older version, I think.
But I don’t have a Fairphone 4 either, I don’t know the specifics 100%, on my devices rollback protection would just force a factory reset, not brick the device.
Perhaps it’s best to wait for somebody who has a Fairphone 4.
I do not know the device but I think that downgrade of Android SPL on what I assume is a locked bootloader is a high risk strategy when I assume what you really need is to fix this issue
As a Customer you can expect support from helpdesk@e.email
I have a Fairphone 4 and would strongly suggest not downgrading the OS after booting. During boot the rollback protection kicks in. I never tried it but according to Fairphone you can brick your device or experience other issues.