That’s a result of occupying a certain canopy layer. Any other plant that occupies that canopy layer can do the same.

But 1) they don't generate electricity 2) they might require care to avoid spreading or attracting bugs (i'm speculating)

The idea to benefit from an energy source at the ecological layer is the main idea IMO.

Generating electricity is a yield to humans. Other plants have other yields.

In an ecosystem, spreading and growing is a feature, not a bug. It means that, as a living system, it self-heals and regenerates. This is better than just being sustainable. A solar panel neither self-heals or regenerate. It in fact, degenerates —- the cells wear out over time, yielding less electricity, and will require replacement at some point.

My question still remains unanswered: what does a solar panel contribute to the ecosystem itself, that is not a result occupying a canopy layer or a yield for humans?

Your viewpoint, as good as it is, is not appropriate here imo. It's a human need being discussed, not an ecosystem one. If you breed the best ecosystem the people will not get tangible benefits, maybe some increase in soil quality, plants resistance, nutrients but is it enough to improve their production and finances ?

At least that's how I see it with my limited information.