How can I automate changing the initial root password?

I am writing a script to migrate droplets from an old OS to a new OS.

The script uses the API to create a new droplet from an image (a snapshot of a partially configured system based on Ubuntu 22 that has already had its initial password changed), and the image has an SSH key for root to allow my script to SCP files to the new server and run some commands via SSH.

The problem is that the SCP and SSH commands fail with the message

You are required to change your password immediately (administrator enforced).
WARNING: Your password has expired.
Password change required but no TTY available.

Is there a way that I can automate changing the initial password to prevent this from happening (presumably via the API), or a different way I should be doing this?

Thanks!