Zend certified PHP/Magento developer

M2: Finding all configurable products that do not have a simple product connected to it

I have removed a bunch of discontinued products (simple products) through CSV.

Most configurable products still have a few simple products attached to it. However, for some, literally all simple products have been removed.

I’m looking for a way to generate a list of all configurable product sku’s, that do not have any simple product attached to it. Has anybody done this before?