The dependencies in Alphas are currently >= 2.0.0 and should be >=2.0.0a0 in order to work with Alphas in cases which are not PEP 440-compliant.

According to https://www.python.org/dev/peps/pep-0440/, >= 2.0.0 should also work with alpha/beta releases (a1/a2) but in some cases it does not (https://apache-airflow.slack.com/archives/C0146STM600/p1602774750041800) 

Changing to ">=2.0.0a0" should help.
provider_packages/setup_provider_packages.py
cross_providers_dependencies_table = \
        convert_cross_package_dependencies_to_table(
            cross_providers_dependencies,
            base_url="https://github.com/apache/airflow/tree/master/airflow/providers/")
    release_version_no_leading_zeros = strip_leading_zeros_in_calver(current_release_version) \
        if backport_packages else current_release_version
    context: Dict[str, Any] = {
        "ENTITY_TYPES": list(EntityType),
        "PROVIDER_PACKAGE_ID": provider_package_id,
        "PACKAGE_PIP_NAME": get_pip_package_name(provider_package_id, backport_packages),
        "FULL_PACKAGE_NAME": full_package_name,
        "RELEASE": current_release_version,
        "RELEASE_NO_LEADING_ZEROS": release_version_no_leading_zeros,
        "CURRENT_CHANGES_TABLE": changes_table,
        "ADDITIONAL_INFO": get_additional_package_info(provider_package_path=provider_package_path),
        "CROSS_PROVIDERS_DEPENDENCIES": cross_providers_dependencies,
        "CROSS_PROVIDERS_DEPENDENCIES_TABLE": cross_providers_dependencies_table,
        "PIP_REQUIREMENTS": PROVIDERS_REQUIREMENTS[provider_package_id],
        "PIP_REQUIREMENTS_TABLE": pip_requirements_table
    }
    changes_template_name = "BACKPORT_PROVIDERS_CHANGES" if backport_packages else "PROVIDERS_CHANGES"
    current_changes = render_template(template_name=changes_template_name, context=context)
    store_current_changes(provider_package_path=provider_package_path,
                          current_release_version=current_release_version,
                          current_changes=current_changes, backport_packages=backport_packages)
    context['ENTITIES'] = entity_summaries
    context['ENTITY_NAMES'] = ENTITY_NAMES
    all_releases = get_all_releases(provider_package_path, backport_packages=backport_packages)
    context["RELEASES"] = all_releases
    readme = LICENCE