Here is the D8 module I am using to accomplish this function: https://www.drupal.org/project/selective_better_exposed_filters
It depends on better_exposed_filters. https://www.drupal.org/project/better_exposed_filters
It's still in beta, so test locally in your environment first, but it worked well in my testing. It won't create the (selective) filter options when you add filter criteria like you are used to in the old D7 module, but it accomplishes the same function:
Once you have an exposed filter in filter criteria, go to "exposed form style" under advanced then switch to better exposed filters (selective). Click apply
And then to enable it, check the box "show only used terms" down towards the bottom. Click apply.
Edit: If you have multiple exposed filters, you can set them each individually under each "more options for..." or you can set all of them globally at the very bottom of the settings options.
Pretty simple for those of us who aren't comfortable writing our own modules.