(I didn't know where to post)
Done!
My main site reached the "symbolic" threshold of 50% of traffic from mobile devices.
One year ago, it was 30 / 70 (mobile/desktop).
At the beginning of September, I received the notification that this site was now in the mobile first index. This resulted into an immediate ratio of 40 / 70.
Now, it's been 7 days, my traffic is 50 / 50 .
My desktop traffic continues to slightly increase, so it's the mobile one which is increasing much faster.