Hi,
Can you confirm if the Free bus service is still available? According to (
https://www.etihad.com/en/abu-dhabi/stopover):Explore Yas Island and Louvre Abu Dhabi with the free A19 bus service from Abu Dhabi International Airport. If you'd like to explore the city, you can also use the Abu Dhabi public transport service for free. You'll find bus stops outside the departures area.
However the link is dead and I can't find anything about this online.