Around mid-August I submitted my sites to Google's Mobile-friendly checker thingy. Two days later I lost 40% of my traffic POOF! I think they crawled all my sites then in advance of the Sept.20th update so (once again) The Porn Nerd is ahead of the curve. Sigh.
And no, the traffic has not returned despite renewed efforts. I also just checked and indeed saw another dip beginning Sept.20th.