Today, I ran into this issue while trying to use the setup action:

Setting up cabal
  Adding /home/runner/.cabal/bin to PATH
  /home/runner/.ghcup/bin/cabal update
  <repo>/root.json does not have enough signatures signed with the appropriate keys
Error: The process '/home/runner/.ghcup/bin/cabal' failed with exit code 1

The relevant part of the workflow:

      - name: Set up Haskell
        uses: haskell-actions/setup@v2
        id: setup
        with:
          ghc-version: '9.2.8'
          cabal-version: '3.10.1.0'
          cabal-update: true

Before this failure, the job had been working. No changes had been made to the workflow in the repository. This is the failed job: https://github.com/exodrifter/website/actions/runs/16579270664/job/46891198451

I found a related issue on the hackage issue tracker: haskell/hackage-server#547. So, I thought my build would start working if I deleted all of my caches for my repository, but this did not resolve the issue.