LGXerxes I just to point out that if you can reach the point of scanning the passport without the app complaining that you are rooted, the app is "working" in the sense that it would have behaved the same way as stock Android and it is not refusing to work due to detecting something different with GrapheneOS.
That said, which country's passport are you trying to read? Is it failing to read it at all or does it give an error after reading? Can you try to read your passport using ReadID Me to see if that works?
Although MitID claims to support any biometric passport, I have multiple citizenships and the app just works for one passport but does not work for another: it reads the passport but then it shows an error and does not proceed. I know it is the app rejecting the passport and not the passport failing to read because the passport can be read successfully via ReadID.