Can I add an old Droplet to a VPC without changing its IP address?

Droplets created prior to October 2020 cannot be added to a VPC network without changing its IP address. Any Droplets created since then have VPC functionality enabled by default and are added to the region’s default VPC network unless you specified otherwise during the creation process. You can still add Droplets created prior to October 2020 to a VPC network by migrating them using snapshots, but they will not retain the same IP information. If you have a domain name directed to the original Droplet, you’ll need to update its DNS records to point to the new IP address.

All Droplets are assigned IPs that are owned by DigitalOcean, which is headquartered in the US.
Edit your Droplet’s sshd_config file to change its SSH port.
You cannot retain a Droplet’s IPv4 when you transfer the Droplet to a new region. Use a reserved IP address to maintain a static IP address.