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
backport_packages: bool,
                                version_suffix: str = "") -> str:
    """
    Returns release version including optional suffix.
    :param provider_package_id: package id
    :param backport_packages: whether to prepare regular (False) or backport (True) packages
    :param version_suffix: optional suffix (rc1, rc2 etc).
    :return:
    """
    return get_latest_release(
        get_package_path(provider_package_id=provider_package_id),
        backport_packages=backport_packages).release_version + version_suffix
def do_setup_package_providers(provider_package_id: str,