Yes I flew into LGA couple of days ago (from colorado, domestic flight). Enforcement basically exists of one poor hapless soul yelling "PLEASE FILL OUT YOUR QUARANTINE TRAVEL FORM AND SHOW IT TO ME" and about 90% of the people walk past him ignoring him. I waved my phone showing the screenshot of the form at him from about 10 feet and he said okay to me in appreciation of acknowledging his thankless job. He obviously couldn't even see if what I was waving from my phone was a filled out form or my loaded reddit site.

So yeah ... no enforcement it is a complete joke.