And they are under constant threat by nation states. sci-hub hasn't seen new papers in ages.

zlibrary does

https://en.wikipedia.org/wiki/Z-Library

Huh, the search is not amazing but it will have to do. Thanks! Are there others?

The Internet Archive supports full-text search on (AFAIK) its entire scanned book collection, even books that aren't available for borrowing.

This is actually pretty good.

I'd wonder if you'd ever consider putting up a downloadable mirror of their full-text search db?

Build a local index

My problem is finding references I don't know about.