How do I share views on multisite in drupal 8
Multisite sharing works by using the same prefix for certain tables. It's dark magic, especially in 8.x, with the automatically created entity and field tables.

Since all config is stored in the same table, that's not possible.

You could write a custom config storage controller that stores certain config in a shared table, but that seems like a very crazy idea to me.

Configuration can be exported/imported and probably doesn't change that often. There will also be modules like features and others that will make re-using configuration easier.

I would also strongly recommend to consider other options to share your content. I can't imagine that this works reliably in 8.x.