ちなみに
Downloads$ sudo apt-get install xserver-xorg-video-amdgpu_1.2.0-1+b1_amd64.deb
Downloads$ sudo apt-get install xserver-xorg-video-amdgpu-dbg_1.2.0-1+b1_amd64.deb

これもエラーで
Unable locate package xserver-xorg-video-amdgpu_1.2.0-1+b1_amd64.deb
couldnt find any package by glob xserver-xorg-video-amdgpu_1.2.0-1+b1_amd64.deb
couldnt find any package by regex xserver-xorg-video-amdgpu_1.2.0-1+b1_amd64.deb