Retropie
Retropie setup guide for XU4: https://retropie.org.uk/docs/Odroid-XU3-XU4/
Controller could be something like: https://www.hardkernel.com/shop/gamesir-g3w-usb-controller-joystick/. Could also be playstation controller with bluetooth dongle.
For better KVM support might want to check https://robert.penz.name/219/workaround-for-the-ubuntu-problem-with-kvm-switches/
Retro arena setup for XU4 https://www.youtube.com/watch?v=CCrKqNvrpGo&t=133s
Wifi dongle + bluetooth controller?