I've tried to come up with a comprehensive listing of functionalities that have existed in SharePoint 2013 Server, but do not exist in SharePoint 2016 Server. The only MS's material I've hit has been this Feature availability across SharePoint standalone plans, which concerns features. I've also seen (and conducted related) lists of added and improved functionalities, but they don't exactly point out the no-longer available ones.

I'd be happy to be guided towards a comprehensive listing of the discontinued functionalities, but also any observed findings are welcome to be added.