how to get unique device id in flutter

I am building an application on flutter to record the attendance process at my university using the qr code, but I have a problem in terms of reliability, which is:

How do I prevent any student from recording attending his classmate from the same mobile phone, what is the solution in order to obtain reliability.. I was thinking of getting the device identifier such as the "imei" to ensure that the person records his attendance by himself, but it is no longer available now in android 10. What is the solution,

Does There any external device ID?

if you just want something to identify each device, why not hash a student name, and college number.. and store that hash locally, then so that the student gets verified, he will be required to provide that name, number.. and so hash it and check if it is the one that is saved at the first time so in general it will be:

• app asks for the user name, and number..
• The app hashes it using some crypto algorithm (I would recommend sha256)
• when user tries to verify his presence with his device, his name, number gets hashed using the same algorithm and then check if it is the one saved locall, passes.
• when the user is not really presence, any try to verify with his name, number.. will fail, since it will hash it and then it will not match the one that is saved locally

This was my idea if you want to follow an offline approach, using NFC, bleutooth..

if you want a quick online solution, just use Firebase anonymous authentication.