Feed Client - Resource not found 404

Problem

When using the Feed Client, the client raises an exception which shows:

azure.devops.exceptions.AzureDevOpsClientRequestError: The resource cannot be found. Operation returned a 404 status code.

Minimal example:

from msrest.authentication import BasicAuthentication
import os

if __name__ == "__main__":
    org = os.environ.get('AZDO_ORG_SERVICE_URL')
    token = os.environ.get('AZDO_PERSONAL_ACCESS_TOKEN')
    credentials = BasicAuthentication('', token)

    from azure.devops.v6_0.feed.feed_client import FeedClient
    feed_client = FeedClient(base_url=org, creds=credentials)
    feed_client.get_feeds()

Other clients like Core are working without any problems.
The permissions of the token are not limited and I am the owner of my test organization.

Enabling debugging output of logging leads to:
DEBUG:azure.devops.client:API resource location c65009a7-474a-4ad1-8b42-7d852107ef8c is not registered on https://dev.azure.com/[Removed].

Details

Python Version: 3.8.5
Package Version: 6.0.0b4

Start with the minimal FeedClient example using azure.devops.v6_0.feed.feed_client and enable azure.devops.client debug logging to reproduce the unregistered resource-location message. Trace FeedClient.get_feeds and compare it with a working client; done means get_feeds no longer returns the 404 for a valid organization and token.