Quick update regarding Python 3.9 support. The team is making good progress towards adding 3.9 support but there are a still few more tasks to complete related to the Airflow plugin. To reduce potential frustration for new users on Python 3.9, we've yanked old Meltano versions from PyPi and added a warning message for new installs. Going forward, pip will print the following message if you attempt to install with Python 3.9:

WARNING: The candidate selected for download or install is a yanked version: 'meltano' candidate ...

Reason for being yanked: Missing version constraint for Python: <3.9. If you are seeing this message, please reinstall using Python 3.8.x to get the latest version of Meltano.