The latest stackage nightly comes with GHC 9, which enables us to add linear-base to Stackage. Both our library, test and benchmark dependencies compile on that nightly (#332).

Before we add it to Stackage, here're the questions that come to my mind:

• I think @aspiwack would be the maintainer (same as for Hackage), but it would be good to confirm before I send a PR using his name :).
• Whether we should submit the current version, or wait until we release the next one. Since it is not a LTS snapshot yet, I don't think there's much reason waiting until our next release.