[Apply Image to layer mask]

I have a Photoshop workflow that uses Apply Image on a layer mask to punch out text from a white field.

Basically, what I do is:

1) Open the PSD.
2) Edit a text layer to make the changes I need. The text is in black.
3) Fill the layer mask with white.
4) Apply the text layer to the layer mask in Multiply mode, 100% opacity.

The result is that the text is erased from the layer that it's applied to, allowing the background to show through. This method does not appear to work in Affinity Photo: nothing happens to the layer with the mask when I apply the text layer as an image. How do I get there form here?