publish-unit-test-result-action: Error while hiding comments in PullReq on GitHub Enterprise

Using GitHub Enterprise Server 3.0.0.

Workflow file (relevant parts):

name: Java CI with Maven

on:
  push:
    branches: [ master ]
  pull_request:
    branches: [ master ]

jobs:
  build:
    runs-on: [ ... ]
    steps:
    - uses: actions/checkout@v2

    - name: Set up JDK 11
      uses: actions/setup-java@v1
      with:
        java-version: 11

    - name: Build with Maven
      run: ./mvnw -B verify --file pom.xml

    - name: Publish Unit Test Results
      uses: EnricoMi/publish-unit-test-result-action@v1.9
      if: always()
      with:
        files: target/surefire-reports/**/*.xml
      env:
        GITHUB_API_URL: https://<our.fqdn.here>/api/v3/

Error received:

Run EnricoMi/publish-unit-test-result-action@v1.9
  with:
    files: target/surefire-reports/**/*.xml
    github_token: ***
    check_name: Unit Test Results
    hide_comments: all but latest
    comment_on_pr: true
    pull_request_build: merge
    check_run_annotations: all tests, skipped tests
    log_level: INFO
  env:
    JAVA_HOME_11.0.10_x64: /home/runner/_work/_tool/jdk/11.0.10/x64
    JAVA_HOME: /home/runner/_work/_tool/jdk/11.0.10/x64
    JAVA_HOME_11_0_10_X64: /home/runner/_work/_tool/jdk/11.0.10/x64
    GITHUB_API_URL: https://<our.fqdn.here>/api/v3/
/usr/bin/docker run --name b1cbc511eb0319cad24c82bd9c7f0910960709_aaa4bd --label b1cbc5 --workdir /github/workspace --rm -e JAVA_HOME_11.0.10_x64 -e JAVA_HOME -e JAVA_HOME_11_0_10_X64 -e GITHUB_API_URL -e INPUT_FILES -e INPUT_GITHUB_TOKEN -e INPUT_COMMIT -e INPUT_CHECK_NAME -e INPUT_COMMENT_TITLE -e INPUT_REPORT_INDIVIDUAL_RUNS -e INPUT_DEDUPLICATE_CLASSES_BY_FILE_NAME -e INPUT_HIDE_COMMENTS -e INPUT_COMMENT_ON_PR -e INPUT_PULL_REQUEST_BUILD -e INPUT_TEST_CHANGES_LIMIT -e INPUT_CHECK_RUN_ANNOTATIONS -e INPUT_CHECK_RUN_ANNOTATIONS_BRANCH -e INPUT_LOG_LEVEL -e HOME -e GITHUB_JOB -e GITHUB_REF -e GITHUB_SHA -e GITHUB_REPOSITORY -e GITHUB_REPOSITORY_OWNER -e GITHUB_RUN_ID -e GITHUB_RUN_NUMBER -e GITHUB_RETENTION_DAYS -e GITHUB_ACTOR -e GITHUB_WORKFLOW -e GITHUB_HEAD_REF -e GITHUB_BASE_REF -e GITHUB_EVENT_NAME -e GITHUB_SERVER_URL -e GITHUB_GRAPHQL_URL -e GITHUB_WORKSPACE -e GITHUB_ACTION -e GITHUB_EVENT_PATH -e GITHUB_ACTION_REPOSITORY -e GITHUB_ACTION_REF -e GITHUB_PATH -e GITHUB_ENV -e RUNNER_OS -e RUNNER_TOOL_CACHE -e RUNNER_TEMP -e RUNNER_WORKSPACE -e ACTIONS_RUNTIME_URL -e ACTIONS_RUNTIME_TOKEN -e GITHUB_ACTIONS=true -e CI=true -v "/var/run/docker.sock":"/var/run/docker.sock" -v "/home/runner/_work/_temp/_github_home":"/github/home" -v "/home/runner/_work/_temp/_github_workflow":"/github/workflow" -v "/home/runner/_work/_temp/_runner_file_commands":"/github/file_commands" -v "/home/runner/_work/<workspace.folder.redacted>/<workspace.folder.redacted>":"/github/workspace" b1cbc5:11eb0319cad24c82bd9c7f0910960709
2021-03-09 12:16:57 +0000 - publish-unit-test-results -  INFO - reading target/surefire-reports/**/*.xml
2021-03-09 12:16:57 +0000 - publish.publisher -  INFO - publishing success results for commit 421157be393553a7c6b3bde525dce2bb41305ba1
2021-03-09 12:16:57 +0000 - publish.publisher -  INFO - creating check
2021-03-09 12:16:58 +0000 - publish.publisher -  INFO - creating comment
Traceback (most recent call last):
  File "/action/publish_unit_test_results.py", line 181, in <module>
    main(settings)
  File "/action/publish_unit_test_results.py", line 67, in main
    Publisher(settings, gh, gha).publish(stats, results.case_results, conclusion)
  File "/action/publish/publisher.py", line 56, in publish
    self.hide_all_but_latest_comments(pull)
  File "/action/publish/publisher.py", line 354, in hide_all_but_latest_comments
    comments = self.get_pull_request_comments(pull)
  File "/action/publish/publisher.py", line 284, in get_pull_request_comments
    "POST", f'{self._settings.api_url}/graphql', input=query
  File "/usr/local/lib/python3.6/site-packages/github/Requester.py", line 317, in requestJsonAndCheck
    verb, url, parameters, headers, input, self.__customConnection(url)
  File "/usr/local/lib/python3.6/site-packages/github/Requester.py", line 340, in __check
    raise self.__createException(status, responseHeaders, output)
github.GithubException.UnknownObjectException: 404 {"message": "Not Found", "documentation_url": "https://docs.github.com/enterprise/3.0/rest"}

Note that test results themself are visible within GitHub Actions output - this part works correctly

Is GH Enterprise supported? Looking at code I’m not sure if GITHUB_API_URL is supported from environment variables (not a Python expert). Same error occurs without GITHUB_API_URL set in step. Or maybe this is issue with action itself?