Some years ago I saw a tutorial (can t remember where )on how to have a standard After Effects lens flare with alpha, without any blending mode.

Render a lens flare with alpha

The combination of the effects channel blur,remove color mapping, and the standard lens flare can give the lens flare on a transparent background without blending mode.
Sometimes you can’ t or don t want to have a blending mode for your layer, so here is the preset:
Drag and drop the preset in your preset folder, and apply it on a black solid.
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