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
entity_type: EntityType,
        entities: Set[str],
        wrong_entities: List[Tuple[type, str]],
        full_package_name: str) -> EntityTypeSummary:
    """
    Splits the set of entities into new and moved, depending on their presence in the dict of objects
    retrieved from the test_contrib_to_core. Updates all_entities with the split class.
    :param entity_type: type of entity (Operators, Hooks etc.)
    :param entities: set of entities found
    :param wrong_entities: wrong entities found for that type
    :param full_package_name: full package name
    :return:
    """
    dict_of_moved_classes = MOVED_ENTITIES[entity_type]
    new_entities = []
    moved_entities = {}
    for obj in entities:
        if obj in dict_of_moved_classes:
            moved_entities[obj] = dict_of_moved_classes[obj]
            del dict_of_moved_classes[obj]