PetDragonPro?
Together with this update, I have released PetDragonPro which is a new and improved version of this plugin with a seamless upgrade process, go check it out! This update also contains some new stuff:

• The plugin is now properly able to work with 1.17+ asynchronous entity loading and now longer relies on a workaround.
• Added extra safeguards to prevent PetDragons from turning 'rogue' by turning into default Enderdragons.
• Added the new setting eggs-abide-by-max-dragons to choose whether PetDragon spawn eggs will respect the maximum amount of dragons per player setting. Keep in mind that dragons are still only tracked in loaded dragons, which is resolved in PetDragonPro.
• Lots of code quality refactoring, aligning the codebase largely with the premium version.
• Removed the plugin-prefix setting.

How to update?
Download the jar file from the top of this page and put it in your plugins folder. Make sure to remove the previous version of this plugin. Now restart (not reload) your server and you are done!