The Ocean Cleanup immediately comes to mind. I very much doubt that they're even slightly "sustainable" in a financial sense, but their engineering and logistics efforts seem to be serious, and outcomes meaningful.

And I've seen various cottage industries in the developing world grow out of/highlighted by Precious Plastic - ones who provide perhaps 5-30 jobs in poor and polluted areas of the world. A warehouse, some crude but effective machinery for processing the waste.

If I wanted to spend 100k on plastic recycling, I’d start a company with a viable business model. The most probable business model would be shaming big companies into paying me for green washing, so hiring great marketing talent would be top priority. Getting the first companies on board to fund further development would be second.