(and changed the // to lib.recursiveUpdate)

Just in case, this doesn't merge lists

How about

  # Package sets to evaluate whole
  # Derivations from these package sets are selected based on the value
  # of their meta.{hydraPlatforms,platforms,badPlatforms} attributes
  autoPackageSets = builtins.filter (lib.strings.hasPrefix "cudaPackages") (builtins.attrNames pkgs);
  autoPackagePlatforms = lib.genAttrs autoPackageSets (pset: packagePlatforms pkgs.${pset});

  # Explicitly select additional packages to also evaluate
  # The desired platforms must be set explicitly here
  explicitPackagePlatforms = (
    # This comment prevents nixfmt from changing the indentation level, lol
    {
      blah = linux;
      ...
    });
  
  # Explicitly specified platforms take precedence over the platforms
  # automatically inferred by release-lib.packagePlatforms
  allPackagePlatforms = lib.recursiveUpdate autoPackagePlatforms explicitPackagePlatforms;
  jobs = mapTestOn allPackagePlatforms;

How about

  # Package sets to evaluate whole
  # Derivations from these package sets are selected based on the value
  # of their meta.{hydraPlatforms,platforms,badPlatforms} attributes
  autoPackageSets = builtins.filter (lib.strings.hasPrefix "cudaPackages") (builtins.attrNames pkgs);
  autoPackagePlatforms = lib.genAttrs autoPackageSets (pset: packagePlatforms pkgs.${pset});

  # Explicitly select additional packages to also evaluate
  # The desired platforms must be set explicitly here
  explicitPackagePlatforms =
    # This comment prevents nixfmt from changing the indentation level, lol
    {
      blah = linux;
      ...
    };
  
  # Explicitly specified platforms take precedence over the platforms
  # automatically inferred by release-lib.packagePlatforms
  allPackagePlatforms = lib.recursiveUpdate autoPackagePlatforms explicitPackagePlatforms;
  jobs = mapTestOn allPackagePlatforms;

How about

  # Package sets to evaluate whole
  # Derivations from these package sets are selected based on the value
  # of their meta.{hydraPlatforms,platforms,badPlatforms} attributes
  autoPackageSets = builtins.filter (lib.strings.hasPrefix "cudaPackages") (builtins.attrNames pkgs);
  autoPackagePlatforms = lib.genAttrs autoPackageSets (pset: packagePlatforms pkgs.${pset});

  # Explicitly select additional packages to also evaluate
  # The desired platforms must be set explicitly here
  explicitPackagePlatforms =
    # This comment prevents nixfmt from changing the indentation level, lol
    {
      blah = linux;
      ...
    };
  
  # Explicitly specified platforms take precedence over the platforms
  # automatically inferred in autoPackagePlatforms
  allPackagePlatforms = lib.recursiveUpdate autoPackagePlatforms explicitPackagePlatforms;
  jobs = mapTestOn allPackagePlatforms;

Any ideas why tensorrt from 24.11 is failing to build? I downloaded and imported the sources into nix store as instructed, but it doesn't want to unpack it.

$ nix log /nix/store/nxmsg8d5w8rljhigv5yaqhrsblzvdndi-python3.12-tensorrt-10.3.0.26.drv
warning: The interpretation of store paths arguments ending in `.drv` recently changed. If this command is now failing try again with '/nix/store/nxmsg8d5w8rljhigv5yaqhrsblzvdndi-python3.12-tensorrt-10.3.0.26.drv^*'
Sourcing python-remove-tests-dir-hook
Sourcing python-catch-conflicts-hook.sh
Sourcing python-remove-bin-bytecode-hook.sh
Sourcing wheel setup hook
Sourcing pypa-install-hook
Using pypaInstallPhase
Sourcing python-imports-check-hook.sh
Using pythonImportsCheckPhase
Sourcing python-namespaces-hook
Sourcing python-catch-conflicts-hook.sh
Sourcing auto-add-driver-runpath-hook
Using autoAddDriverRunpath
Sourcing fix-elf-files.sh
Running phase: unpackPhase
@nix { "action": "setPhase", "phase": "unpackPhase" }
tar: TensorRT-10.3.0.26/python/tensorrt-10.3.0.26-cp312-none-linux_x86_64.whl: Not found in archive
tar: Exiting with failure status due to previous errors