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
EntityType.Secrets: [0, 0],
}
OPERATORS_PATTERN = r".*Operator$"
SENSORS_PATTERN = r".*Sensor$"
HOOKS_PATTERN = r".*Hook$"
SECRETS_PATTERN = r".*Backend$"
TRANSFERS_PATTERN = r".*To[A-Z0-9].*Operator$"
WRONG_TRANSFERS_PATTERN = r".*Transfer$|.*TransferOperator$"
ALL_PATTERNS = {
    OPERATORS_PATTERN,
    SENSORS_PATTERN,
    HOOKS_PATTERN,
    SECRETS_PATTERN,
    TRANSFERS_PATTERN,
    WRONG_TRANSFERS_PATTERN,
}
EXPECTED_SUFFIXES: Dict[EntityType, str] = {
    EntityType.Operators: "Operator",
    EntityType.Hooks: "Hook",
    EntityType.Sensors: "Sensor",
    EntityType.Secrets: "Backend",
    EntityType.Transfers: "Operator",
}
def get_source_airflow_folder() -> str:
    """
    Returns source directory for whole airflow (from the main airflow project).
    :return: the folder path
    """
    return os.path.abspath(os.path.join(dirname(__file__), os.pardir))
def get_source_providers_folder() -> str: