Seem to be missing some step in creating photographic text. Using MAC and GIMP 2.10.12

Imported image as base layer; Created a new transparent Layer as the 2nd Layer and placed a Gradient on it and set opacity to 70%; 3rd layer is text layer. Desire is to have the image base layer show through the text.

Once above completed - I went to the Base (Image) Layer and selected "Add Alpha Channel". Then went to Text Layer and selected "Alpha to Selection". This places the dotted lines around the text. However this is where I'm confused. Seems you are suppose to go to one of the Layers and select "Select/Invert" and on the same layer or a different Layer hit Delete on the Mac keyboard. I've tried multiple combinations of this and cannot get the image background to show through the Text.

You are almost there. I think this is what you want. Keep an eye on the Layers dialogue I detached.

Three layers - base - gradient - text Do not bother with opacity, set that later. (1)

The text layer will be set to the size of the characters so make it the same size as the canvas. Layer -> Layer to Image size. (2) This does lose the text property so make sure It is what you want as a final result.

On the 'text' make the selection. Layer -> Transparency -> Alpha to Selection. This is the text shape and you need the remainder so Select -> Invert.

Now you can turn off the text layer visibility and go to the Gradient layer (3) and cut the selection Edit -> Cut leaving the text shape in the gradient layer (4)

Now adjust the opacity of the gradient layer to suit (5)

As with everything Gimp, there is a better way. Using a layer mask

Starting with the same three layers. Use the text layer to make a selection. Layer -> Transparency -> Alpha to selection. (1)

Hate this mailing list format so screenshot: https://i.imgur.com/188coxa.jpg

Turn the text visibility off, move down to the gradient layer then. Layer -> Mask -> Add layer mask. In the dialogue choose the selection option (2)

screenshot: https://i.imgur.com/Cl0IQx0.jpg

Turn the selction off, Select -> None, adjust the opacity of the gradient layer (3)

screenshot: https://i.imgur.com/6aKXRE7.jpg

Re-reading your post just confused myself.

Did this some time ago maybe this is your aim

see: https://www.gimp-forum.net/Thread-Cut-Out-Text