Or may I use Openhab and not Home Assistant?

Hello,
I have clean and unused Raspberry Pi 4 + old screen from notebook and HDMI adapter for this screen.

I would like to create a magic mirror to show info from my Xiaomi smart ecosystem (temperatues, lights, etc.)
In what order should I install MagicMirror² and Home Assistant?
I have also PIR sensor - how can I turn on/off screen of magic mirror with this sensor?

Thank you in advance