Hello, @wantsomebananas

A similar question was asked before in the community. I will link the original question so you can check it - https://www.digitalocean.com/community/questions/how-rdns-technically-works-in-digital-ocean

DigitalOcean automatically configures the reverse dns entry (PTR) on their end. It will be the hostname you choose when you set up your dropplet. You can change/check this in the control panel by selecting your dropplet, then settings, then rename. As it says, changing the name there will update the PTR but not the hostname of the system, that is something you will need to do, instructions for that vary depending on the system you have installed.

Hope this helps! Let me know if you have any questions.

Regards,
Alex