Try #1713:

ci.nix

@@ -31,10 +31,12 @@
     # Update supported-ghc-versions.md to reflect any changes made here.
     nixpkgs.lib.optionalAttrs (nixpkgsName == "R2205") {
       ghc865 = false;
+      ghc810420210212 = false; # TODO remove when plutus no longer uses this.
       ghc8107 = false;
     } // nixpkgs.lib.optionalAttrs (nixpkgsName == "unstable") {
       ghc865 = false;
       ghc884 = false; # Native version is used to boot 9.0.1
+      ghc810420210212 = false; # TODO remove when plutus no longer uses this.
       ghc8107 = true;
       ghc902 = false;
       ghc924 = true;
@@ -43,7 +45,7 @@
     nixpkgs.lib.filter (v:
         # We have less x86_64-darwin build capacity so build fewer GhC versions
         (v != "x86_64-darwin" || (
-           !__elem compiler-nix-name ["ghc8104" "ghc810420210212" "ghc8105" "ghc8106" "ghc901" "ghc921" "ghc922"]))
+           !__elem compiler-nix-name ["ghc8104" "ghc8105" "ghc8106" "ghc901" "ghc921" "ghc922"]))
       &&
         # aarch64-darwin requires ghc 8.10.7
         (v != "aarch64-darwin" || (

release.nix

@@ -1,7 +1,7 @@
 # 'supportedSystems' restricts the set of systems that we will evaluate for. Useful when you're evaluating
 # on a machine with e.g. no way to build the Darwin IFDs you need!
 { supportedSystems ? [ "x86_64-linux" "x86_64-darwin" ]
-, ifdLevel ? 3
+, ifdLevel ? 2
 , include ? (compiler-nix-name: true)
 , checkMaterialization ? false }: