You're totally right. I couldn't see any mac address on settings. and here comes my next question as I haven't touched anything regarding EFS. With that said, I don't have any backup
From online search, it seems requires to flash back to Oxygen OS - https://forum.xda-developers.com/t/...y-are-and-how-to-get-it-back-if-lost.3307793/ - Is it good idea to do that and is there any where I can get the official Oxygen files? It's kinda too old at this stage.