This mobile first indexing launch, which supposedly began rolling out a month ago to a wider set of sites, has mostly gone completely unnoticed. I saw no one post that they received Search Console notifications or shown any other signs of the rollout.
But that does not mean it did not roll out to at least some sites.
John Mueller of Google at BrightonSEO said, according to Kenichi Suzuki, that that batch was "small" but in the upcoming weeks, there will be another rollout that is "bigger." Here is Kenichi Suzuki's tweet covering it:
.@JohnMu confirmed Mobile first index began a month ago even though nobody seems to have received the notification. It was run by a small batch. The next batch will be bigger and be run soon (next week or so?) #BrightonSEO
— Kenichi Suzuki?鈴木謙一 (@suzukik) April 27, 2018
So if anyone gets these notifications soon or shows other signs of them being crawled using the mobile-first indexing process, do let us know.
For now, I have yet to see anyone definitively say they are now being indexed in the mobile-first indexing manner.
Forum discussion at Twitter.