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
-> Dict[EntityType, EntityTypeSummary]:
    """
    Gets summary of the package in the form of dictionary containing all types of entities
    :param full_package_name: full package name
    :param imported_classes: entities imported_from providers
    :return: dictionary of objects usable as context for JINJA2 templates - or None if there are some errors
    """
    from airflow.hooks.base_hook import BaseHook
    from airflow.models.baseoperator import BaseOperator
    from airflow.secrets import BaseSecretsBackend
    from airflow.sensors.base_sensor_operator import BaseSensorOperator
    all_verified_entities: Dict[EntityType, VerifiedEntities] = {EntityType.Operators: find_all_entities(
        imported_classes=imported_classes,
        base_package=full_package_name,
        sub_package_pattern_match=r".*\.operators\..*",
        ancestor_match=BaseOperator,
        expected_class_name_pattern=OPERATORS_PATTERN,
        unexpected_class_name_patterns=ALL_PATTERNS - {OPERATORS_PATTERN},
        exclude_class_type=BaseSensorOperator,
        false_positive_class_names={
            'CloudVisionAddProductToProductSetOperator',
            'CloudDataTransferServiceGCSToGCSOperator',
            'CloudDataTransferServiceS3ToGCSOperator',
            'BigQueryCreateDataTransferOperator',