For some reason, view rows no longer get those handy numbered classes and even/odd you can use to format row based on placement in the results. All rows are given "views-row" only. Not helpful.
I was able to fix this by copying the Views twig template to my theme's template/views directory. In my case, I am using an unformatted list, so I used views-view-unformatted.html.twig.