Photoshop request - Alpha Transparency

To get an Alpha cahnnel, you could Stamp Visible Control+Alt+Shift+E), load the resulting layer's transparency as a selection, and save this selection as an Alpha.

Another approach would be to Control+click on the thumbnail for the RGB composite in the Channels panel, to load the luminosity as a selection. Enter Quick Mask mode (Q), Press Control+I to invert, and use Image > Adjustments  > Levels to adjust the transition. Exit Quick Mask, and save the selection as an Alpha..

You can do this using the blending sliders. Make sure your image is a regular layer, not the Background layer, and but a new blank layer below it. Right click on the image layer, and click Blending Options. In the "Blend if" area, chose Gray. Drag the white triangle leftward. If you Alt+drag one side of the triangle, you can split it to get a transition range.

Have you tried any of the select subject or remove background features in the new Photoshop?
It auto creates a mask.

https://www.adobe.com/creativecloud/photography/discover/background-remover.html 

>wonderful if it could be added

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