Not 3.0 yet, but Airflow is a very, very mature project I'd say.
It was released Oct. 2014, joined Apache Foundation in 2016, became a top level project in 2019.
Check the release notes/ blog post and you'll see the amount of people involved.
In this release, some, but not all features are genuinely new without past dependencies, but I didn't spot major breaking changes.
I'd confidently go ahead, esp. in greenfield.
Might be a bit more muddy to migrate from 2.X to 3 atm.
