you could do things blindly, like write ur password and try to get any sign after it of ur os running, like get a terminal (im using ubuntu mate, where its a matter of pressing ctrl+alt+t, but i think its not enabled by default on debian, but there should be a shorthand for it i think) and then play a sound or write on any media or whatever… or even, you can play with ctrl+alt+1 for tty1 and ctrl+alt+7 for switching back to “graphical mode”. (maybe its easier to just obtain a hdmi monitor for testing, or messing with the hw 
)
now i gotta go, maybe ill b back like after a hour for a few mins, but after that ill disappear for some hours. good luck buddy! 