Unable to push nuGet packages to GitLab with dotnet CLI due to Unauthorized error

GitLab now supports nuget public and private feed repository. I've got a public project (e.g: https://gitlab.com/sunnyatticsoftware/sasw-test-support) I create an access token for my user with api and write_repository (e.g: AAABBBCCCDDD)

I create a group variable in my CI/CD: SASW_API_ACCESS_TOKEN: AAABBBCCCDDD. All normal.

Then I create the multi stage CI/CD script to build, pack and publish. When attempting to publish the nuGet package with the following: dotnet nuget push **/*.nupkg --source https://gitlab.com/api/v4/projects/17141695/packages/nuget/index.json --api-key AAABBBCCCDDD --skip-duplicate

I get the error:

info : Pushing Sasw.TestSupport.2.0.2.nupkg to 'https://gitlab.com/api/v4/projects/17141695/packages/nuget'...
info :   PUT https://gitlab.com/api/v4/projects/17141695/packages/nuget/
info :   Unauthorized https://gitlab.com/api/v4/projects/17141695/packages/nuget/ 397ms
error: Response status code does not indicate success: 401 (Unauthorized).
ERROR: Job failed: exit code 1

The documentation doesn't mention anything special, but I notice that when using the (legacy?) nuget CLI it passes a username. Dotnet CLI, however, doesn't support username, just API KEY.

Any idea why this is not working?

This is my CI/CD script:

variables:
  GITLAB_RUNNER_DOTNET_CORE: mcr.microsoft.com/dotnet/core/sdk:3.1
  NUGET_REPOSITORY: https://gitlab.com/api/v4/projects/${CI_PROJECT_ID}/packages/nuget/index.json
  NUGET_API_KEY: $SASW_API_ACCESS_TOKEN
  NUGET_FOLDER_NAME: nupkgs
  NUGET_VERSION_SUFFIX: $SASW_PRERELEASE_SUFFIX

stages:
  - build
  - pack
  - release

#Docker image
image: $GITLAB_RUNNER_DOTNET_CORE

#Jobs
ci:
  stage: build
  script:
    - dotnet restore --no-cache --force
    - dotnet build --configuration Release --no-restore
    #- dotnet vstest test/*UnitTests/bin/Release/**/*UnitTests.dll
    #- dotnet vstest test/*IntegrationTests/bin/Release/**/*IntegrationTests.dll

pack-prerelease:
  stage: pack
  script:
    - dotnet pack *.sln --configuration Release --output $NUGET_FOLDER_NAME --version-suffix $NUGET_VERSION_SUFFIX --include-symbols -p:SymbolPackageFormat=snupkg
  artifacts:
    paths:
    - $NUGET_FOLDER_NAME
    expire_in: 1 week
  except:
    - master

pack-release:
  stage: pack
  script:
    - dotnet pack *.sln --configuration Release --output $NUGET_FOLDER_NAME
  artifacts:
    paths:
    - $NUGET_FOLDER_NAME
    expire_in: 1 week
  only:
    - master

publish-nuget:
  stage: release
  script:
    - dotnet nuget push **/*.nupkg --source $NUGET_REPOSITORY --api-key $NUGET_API_KEY --skip-duplicate

PS: The project is public, so in case it's needed have a look at: https://gitlab.com/sunnyatticsoftware/sasw-test-support/-/jobs/451080235

UPDATE 1: Further verbosity from my local linux console

$ dotnet nuget -v Debug push **/*.nupkg --source https://gitlab.com/api/v4/projects/17141695/packages/nuget/index.json --api-key cBwt5_hidden_ --skip-duplicate
trace: NuGet Command Line Version: 5.4.0.2
info : Pushing Sasw.TestSupport.2.0.2.nupkg to 'https://gitlab.com/api/v4/projects/17141695/packages/nuget'...
info :   PUT https://gitlab.com/api/v4/projects/17141695/packages/nuget/
info :   Unauthorized https://gitlab.com/api/v4/projects/17141695/packages/nuget/ 1159ms
error: Response status code does not indicate success: 401 (Unauthorized).
trace: System.AggregateException: One or more errors occurred. (Response status code does not indicate success: 401 (Unauthorized).)
trace:  ---> System.Net.Http.HttpRequestException: Response status code does not indicate success: 401 (Unauthorized).
trace:    at System.Net.Http.HttpResponseMessage.EnsureSuccessStatusCode()
trace:    at NuGet.Protocol.Core.Types.PackageUpdateResource.EnsureSuccessStatusCode(HttpResponseMessage response, Nullable`1 codeNotToThrow, ILogger logger)
trace:    at NuGet.Protocol.Core.Types.PackageUpdateResource.<>c__DisplayClass23_0.<PushPackageToServer>b__0(HttpResponseMessage response)
trace:    at NuGet.Protocol.HttpSource.ProcessResponseAsync[T](HttpSourceRequest request, Func`2 processAsync, SourceCacheContext cacheContext, ILogger log, CancellationToken token)
trace:    at NuGet.Protocol.Core.Types.PackageUpdateResource.PushPackageToServer(String source, String apiKey, String pathToPackage, Int64 packageSize, Boolean noServiceEndpoint, Boolean skipDuplicate, TimeSpan requestTimeout, ILogger logger, CancellationToken token)
trace:    at NuGet.Protocol.Core.Types.PackageUpdateResource.PushPackageCore(String source, String apiKey, String packageToPush, Boolean noServiceEndpoint, Boolean skipDuplicate, TimeSpan requestTimeout, ILogger log, CancellationToken token)
trace:    at NuGet.Protocol.Core.Types.PackageUpdateResource.PushPackage(String packagePath, String source, String apiKey, Boolean noServiceEndpoint, Boolean skipDuplicate, TimeSpan requestTimeout, ILogger log, CancellationToken token, Boolean isSnupkgPush)
trace:    at NuGet.Protocol.Core.Types.PackageUpdateResource.Push(String packagePath, String symbolSource, Int32 timeoutInSecond, Boolean disableBuffering, Func`2 getApiKey, Func`2 getSymbolApiKey, Boolean noServiceEndpoint, Boolean skipDuplicate, SymbolPackageUpdateResourceV3 symbolPackageUpdateResource, ILogger log)
trace:    at NuGet.Commands.PushRunner.Run(ISettings settings, IPackageSourceProvider sourceProvider, String packagePath, String source, String apiKey, String symbolSource, String symbolApiKey, Int32 timeoutSeconds, Boolean disableBuffering, Boolean noSymbols, Boolean noServiceEndpoint, Boolean skipDuplicate, ILogger logger)
trace:    at NuGet.CommandLine.XPlat.PushCommand.<>c__DisplayClass0_1.<<Register>b__1>d.MoveNext()
trace:    --- End of inner exception stack trace ---
trace:    at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
trace:    at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
trace:    at System.Threading.Tasks.Task`1.get_Result()
trace:    at Microsoft.Extensions.CommandLineUtils.CommandLineApplication.<>c__DisplayClass56_0.<OnExecute>b__0()
trace:    at Microsoft.Extensions.CommandLineUtils.CommandLineApplication.Execute(String[] args)
trace:    at NuGet.CommandLine.XPlat.Program.MainInternal(String[] args, CommandOutputLogger log)