Thanks at lot!1. Any Explorer working with Root is needed (I hope anyone who's in this thread has one).
2. Open the * \ system folder and drop it into it, replacing the original file, already edited by build.prop (unzip it first). After that, set the permission rw - - (i.e., only two checkboxes in the Owner line: Read and Write). Reboot the device and enjoy life)))
This should be built-in or at least linked-pinnted to the top post. I found out about it too late - the model change is not purely cosmetial. The Note9 id is written into all image tags, making image apps apply the wrong settings (like lens correction)
Btw: The rom works fine except except the buggy camera2 api, which makes exposure bracketing and opening camera2 apps like OpenCamera prone to crashes. I know this is free, but wouldn't mind a security update