There are reasons nothing is growing under your pine. Plants under a pine have to deal not only with acid soil, but also competition from tree roots. Shallow-rooted plants or maybe plants in raised beds or containers would probably do best. There might be some strawberries - Alpine, Musk or regular, which would do well there if you prepare a bed for them.

If the pine is really high-branching, you might consider pawpaws, which naturally grow as an understory tree. Not sure how they do with pines.

Pinetree recommends evergreen huckleberry for shade. In their print catalog, they have lists of plants which are shade-tolerant, etc.

Here is a link that might be useful: huckleberries

I'm trying lingonberries as groundcover under my pines. It's too soon to tell how they will work out. Red or blue huckleberries and oregon grapes should work as well.

As I see it unless you go with a pine forest floor plant you are in for trouble. The Pine will soak up almost all of the water and if you put water inside the drip line you can creat problems with fungus.

Maybe self-watering containers would work.

try with Vaccinum, Arbutus,