This is good though it's not clear whether these papers will appear in the PMC Open Access subset (https://pmc.ncbi.nlm.nih.gov/tools/openftlist/) and be bulk downloadable.

I've been doing some work with colleagues at Cambridge and Imperial over the last year on using LLMs to improve evidence synthesis, primarily trying to find papers on the effectiveness of certain Conservation interventions. It's becoming clear that you really need to move beyond screening papers only by title and abstract - there's often information buried deep within papers that can only be found with access to full text. My colleague Anil Madhavapeddy has written a bit about our adventures in trying to ingest full-text academic papers: https://anil.recoil.org/notes/uk-national-data-lib