Filtering on a multivalue daterange field in Drupal 8

What the heck happens?

This discussion of filtering by date doesn’t mention multivalue daterange fields, unfortunately: https://drupal.stackexchange.com/questions/226884/how-to-filter-a-view-by-date-range-start-end

Although in particular this answer on that thread, while handling a different complex case, suggests most anything is possible… https://drupal.stackexchange.com/a/235412/4195

Not-quite-useful references:

Solr-specific

References: