diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 9ba09634a15..eb2700d377a 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -15,6 +15,13 @@ If not, you aren't able to build the testsuite, so you need to disable the defau
 cabal build --project-file=cabal.project.release cabal
 ```
 
+> **Note**
+> If you're using Nix, you might find it convenient to work within a shell that has all the `Cabal` development dependencies:
+> ```
+> $ nix-shell -p cabal-install ghc ghcid haskellPackages.fourmolu_0_12_0_0 pkgconfig zlib.dev
+> ```
+> A Nix flake developer shell with these dependencies is also available, supported solely by the community, through the command `nix develop github:yvan-sraka/cabal.nix`.
+
 The location of your build products will vary depending on which version of
 cabal-install you use to build; see the documentation section
 [Where are my build products?](http://cabal.readthedocs.io/en/latest/nix-local-build.html#where-are-my-build-products)
diff --git a/Cabal-tests/tests/UnitTests/Distribution/Simple/Program/GHC.hs b/Cabal-tests/tests/UnitTests/Distribution/Simple/Program/GHC.hs
index 985c91f8eae..8244285915f 100644
--- a/Cabal-tests/tests/UnitTests/Distribution/Simple/Program/GHC.hs
+++ b/Cabal-tests/tests/UnitTests/Distribution/Simple/Program/GHC.hs
@@ -1,11 +1,16 @@
 module UnitTests.Distribution.Simple.Program.GHC (tests) where
 
+import qualified Data.Map as Map
 import Data.Algorithm.Diff (PolyDiff (..), getDiff)
 import Test.Tasty          (TestTree, testGroup)
 import Test.Tasty.HUnit
 
+import Distribution.System (Platform(..), Arch(X86_64), OS(Linux))
+import Distribution.Types.ParStrat
+import Distribution.Simple.Flag
+import Distribution.Simple.Compiler (Compiler(..), CompilerId(..), CompilerFlavor(..), AbiTag(NoAbiTag))
 import Distribution.PackageDescription (emptyPackageDescription)
-import Distribution.Simple.Program.GHC (normaliseGhcArgs)
+import Distribution.Simple.Program.GHC (normaliseGhcArgs, renderGhcOptions, ghcOptNumJobs)
 import Distribution.Version            (mkVersion)
 
 tests :: TestTree
@@ -38,6 +43,22 @@ tests = testGroup "Distribution.Simple.Program.GHC"
 
             assertListEquals flags options_9_0_affects
         ]
+    , testGroup "renderGhcOptions"
+      [ testCase "options" $ do
+            let flags :: [String]
+                flags = renderGhcOptions
+                  (Compiler
+                      { compilerId = CompilerId GHC (mkVersion [9,8,1])
+                      , compilerAbiTag = NoAbiTag
+                      , compilerCompat = []
+                      , compilerLanguages = []
+                      , compilerExtensions = []
+                      , compilerProperties = Map.singleton "Support parallel --make" "YES" 
+                      })
+                  (Platform X86_64 Linux)
+                  (mempty { ghcOptNumJobs = Flag (NumJobs (Just 4)) })
+            assertListEquals flags ["-j4", "-clear-package-db"]
+        ]        
     ]
 
 assertListEquals :: (Eq a, Show a) => [a] -> [a] -> Assertion
diff --git a/Cabal/src/Distribution/Simple/Program/Builtin.hs b/Cabal/src/Distribution/Simple/Program/Builtin.hs
index 909ecc7e4b6..1f3db0740f3 100644
--- a/Cabal/src/Distribution/Simple/Program/Builtin.hs
+++ b/Cabal/src/Distribution/Simple/Program/Builtin.hs
@@ -347,7 +347,33 @@ greencardProgram :: Program
 greencardProgram = simpleProgram "greencard"
 
 ldProgram :: Program
-ldProgram = simpleProgram "ld"
+ldProgram =
+  (simpleProgram "ld")
+    { programPostConf = \verbosity ldProg -> do
+        -- The `lld` linker cannot create merge (relocatable) objects so we
+        -- want to detect this.
+        -- If the linker does support relocatable objects, we want to use that
+        -- to create partially pre-linked objects for GHCi, so we get much
+        -- faster loading as we do not have to do the separate loading and
+        -- in-memory linking the static linker in GHC does, but can offload
+        -- parts of this process to a pre-linking step.
+        -- However this requires the linker to support this features. Not all
+        -- linkers do, and notably as of this writing `lld` which is a popular
+        -- choice for windows linking does not support this feature. However
+        -- if using binutils ld or another linker that supports --relocatable,
+        -- we should still be good to generate pre-linked objects.
+        ldHelpOutput <-
+          getProgramInvocationOutput
+            verbosity
+            (programInvocation ldProg ["--help"])
+            -- In case the linker does not support '--help'. Eg the LLVM linker,
+            -- `lld` only accepts `-help`.
+            `catchIO` (\_ -> return "")
+        let k = "Supports relocatable output"
+            v = if "--relocatable" `isInfixOf` ldHelpOutput then "YES" else "NO"
+            m = Map.insert k v (programProperties ldProg)
+        return $ ldProg{programProperties = m}
+    }
 
 tarProgram :: Program
 tarProgram =
diff --git a/Cabal/src/Distribution/Simple/Program/GHC.hs b/Cabal/src/Distribution/Simple/Program/GHC.hs
index 1f525fd9f39..537e008c17f 100644
--- a/Cabal/src/Distribution/Simple/Program/GHC.hs
+++ b/Cabal/src/Distribution/Simple/Program/GHC.hs
@@ -701,7 +701,7 @@ renderGhcOptions comp _platform@(Platform _arch os) opts
                 if jsemSupported comp
                   then ["-jsem " ++ name]
                   else []
-              Flag (NumJobs n) -> ["-j" ++ show n]
+              Flag (NumJobs n) -> ["-j" ++ maybe "" show n]
             else []
         , --------------------
           -- Creating libraries
diff --git a/cabal-install/cabal-install.cabal b/cabal-install/cabal-install.cabal
index d20db6ced51..dfc4a2d9ec5 100644
--- a/cabal-install/cabal-install.cabal
+++ b/cabal-install/cabal-install.cabal
@@ -250,9 +250,9 @@ library
     if flag(lukko)
       build-depends: lukko >= 0.1 && <0.2
 
-   -- pull in process version with fixed waitForProcess error
-   if impl(ghc >=8.2)
-     build-depends: process >= 1.6.15.0
+    -- pull in process version with fixed waitForProcess error
+    if impl(ghc >=8.2)
+      build-depends: process >= 1.6.15.0
 
 
 executable cabal
diff --git a/cabal-install/src/Distribution/Client/Nix.hs b/cabal-install/src/Distribution/Client/Nix.hs
index 34a12f9157b..0a8d6a5c195 100644
--- a/cabal-install/src/Distribution/Client/Nix.hs
+++ b/cabal-install/src/Distribution/Client/Nix.hs
@@ -47,7 +47,7 @@ import Distribution.Simple.Program
   , simpleProgram
   )
 import Distribution.Simple.Setup (fromFlagOrDefault)
-import Distribution.Simple.Utils (debug, existsAndIsMoreRecentThan)
+import Distribution.Simple.Utils (debug, existsAndIsMoreRecentThan, warn)
 
 import Distribution.Client.Config (SavedConfig (..))
 import Distribution.Client.GlobalFlags (GlobalFlags (..))
@@ -144,6 +144,9 @@ nixShell verb dist globalFlags config go = do
       findNixExpr globalFlags config >>= \case
         Nothing -> go
         Just shellNix -> do
+          -- Nix integration never worked with cabal-install v2 commands ...
+          warn verb "Nix integration has been deprecated and will be removed in a future release. You can learn more about it here: https://cabal.readthedocs.io/en/latest/nix-integration.html"
+
           let prog = simpleProgram "nix-shell"
           progdb <- configureOneProgram verb prog
 
diff --git a/cabal-install/src/Distribution/Client/Setup.hs b/cabal-install/src/Distribution/Client/Setup.hs
index 6a96fb54640..44224d9559b 100644
--- a/cabal-install/src/Distribution/Client/Setup.hs
+++ b/cabal-install/src/Distribution/Client/Setup.hs
@@ -502,17 +502,17 @@ globalCommand commands =
               )
               ""
               ["nix"] -- Must be empty because we need to return PP.empty from viewAsFieldDescr
-              "Nix integration: run commands through nix-shell if a 'shell.nix' file exists (default is False)"
+              "[DEPRECATED] Nix integration: run commands through nix-shell if a 'shell.nix' file exists (default is False)"
           , noArg
               (Flag True)
               []
               ["enable-nix"]
-              "Enable Nix integration: run commands through nix-shell if a 'shell.nix' file exists"
+              "[DEPRECATED] Enable Nix integration: run commands through nix-shell if a 'shell.nix' file exists"
           , noArg
               (Flag False)
               []
               ["disable-nix"]
-              "Disable Nix integration"
+              "[DEPRECATED] Disable Nix integration"
           ]
       , option
           []
diff --git a/doc/nix-integration.rst b/doc/nix-integration.rst
index 6edf595b6f0..5d4fa695cd4 100644
--- a/doc/nix-integration.rst
+++ b/doc/nix-integration.rst
@@ -1,6 +1,15 @@
 Nix Integration
 ===============
 
+.. warning::
+
+    Nix integration has been deprecated and will be removed in a future release.
+
+    The original mechanism can still be easily replicated with the following commands:
+
+    - for a ``shell.nix``: ``nix-shell --run "cabal ..."``
+    - for a ``flake.nix``: ``nix develop -c cabal ...``
+
 .. note::
 
     This functionality doesn't work with nix-style builds.