@fragmentzero In order for you to see Device Manager in the Package Manager, You to check “Enable Preview Packages” in Project Settings>Package Manager.
I believe it is now pre-included with recent versions of Unity. Make sure you have build settings set to Android, restart your editor and you should be able to see the simulator in game view.
U can install device simulator package, first you download from github, then install it from import new asset , find file json then klik. just wait, device simulator will installed in your unity