I have the exact same issue on my brand new R10 5900 running 2.1.2 I have tried everything and it just doesn’t enter into the bios gives a black screen and gets stuck until I power it off with the button  Note:/ Duplicate post.  Issue was solved here.
I am trying to access the BIOS of my R10 by hitting F2 as suggested. It does not work. The computer just freezes and stops on a black screen after booting. My BIOS was the 1.0.7 I decided to upgrade to 1.0.8 No change. The computer still freezes if I hit F2 and nothing happens. Has anyone any idea how to solve the problem?
Aurora R10, cannot access BIOS hitting F2?