log into android and poweroff via any "power menu" apk inside android
put you armbian flashed sd (try balena etcher) and use half of ear cleaning cotton bud's stick to put and press in AV/audio port ; keep pressing then put dc power - until anything comes in hdmi out-you can try 3sec 8sec method; put bud and press count 3 put dc in while pressing count upto 8 then let go