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
"""
    Converts PIP requirement list to a markdown table.
    :param requirements: requirements list
    :return: markdown-formatted table
    """
    from tabulate import tabulate
    headers = ["PIP package", "Version required"]
    table_data = []
    for dependency in requirements:
        found = re.match(r"(^[^<=>~]*)([^<=>~]?.*)$", dependency)
        if found:
            package = found.group(1)
            version_required = found.group(2)
            table_data.append((package, version_required))
        else:
            table_data.append((dependency, ""))
    return tabulate(table_data, headers=headers, tablefmt="pipe")
def convert_cross_package_dependencies_to_table(