Google Books was a great resource until the lawyers got involved. I was able to find and download (one screenshot at a time) a rare family history. The author died 100 years ago. The published disappeared 80 years ago. But now Google has locked it behind a limited preview.
Google probably has the best collection of high quality scans, followed by the Hathi Trust. None of which are useable by anyone outside of those systems.
Does Anna's Archive have it now? They scrape tons of sources, Google Books and HathiTrust included.
A lot of Hathi is locked behind university and library access restrictions. I sometimes have to track down students or someone who has a local library card to get items I need.
Not that I know of, I did upload the PDF to the original libgen but that particular domain has disappeared now.
I agree they're the best currently available, but a lot of their scans are straight garbage and need to be redone.
A garbage scan is better than no book at all. Fortunately the book I needed was a clean scan.