`./scripts` is so far the most popular, it’s just what I have seen across projects.

`./script` was proposed (and is still used?) by GitHub. See github.com/github/scripts-to-r

`./build` is sometimes used because these scripts are often executed at build-time (and thus in CI)

Another thing I’ve seen were scripts in the repository root, but for the sake of the poll let’s assume there are too many scripts for this.