Sustainability does not mean defending the non-human world from human expansion. Instead, it has come to mean sustaining human civilisation at the comfort level which the world’s rich people feel is their right.
In order to be truly sustainable, solar panels must offset the harms done in their creation and disposal, as well as enough energy to replace themselves at the end of their lifetime. Not only are solar panels not sustainable, but they likely never will be.
If your question is “How to we scale up sustainable ‘solutions’ so we can keep living the way we are?”, the answer is, “We don’t.”