How to temporarily run a secondary SSH server on a separate port

How do you run an SSH daemon on a different port other than the standard 22?

I screwed up something with my SSH configuration on a cloud VM, so that now SSH always prompts me for a password. My early attempts to fix this locked me out, forcing me to umount the disk, mount it inside a working VM, and fix the files to a known working state. However, it’s still forcing me to enter a password.

I’d like to update my /etc/ssh/sshd_config and restart the main ssh daemon, which I can test against, while still having another one running, using the old configuration, that I can use to revert the configuration in case the first one locks me out. How would I do this, specifically on Ubuntu?