wip: try image with ci user + sudo

.forgejo/workflows/check.yml

@@ -1,7 +1,7 @@
 name: Flake checks
 on: [pull_request]
 env:
-  USER: root
+  USER: ci
 
 jobs:
   Check:
@@ -9,9 +9,10 @@ jobs:
     steps:
       - name: Install dependencies
         run: |
-          apt-get update && apt-get install --yes sudo zstd && groupadd nixbld
+          sudo apt-get update && sudo apt-get install --yes zstd jq
       - uses: https://github.com/nixbuild/nix-quick-install-action@v26
         with:
+          nix_version: 2.19.2
           nix_conf: |
             substituters = https://cache.nixos.org/ https://nix-community.cachix.org
             trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs=