Creating Jira Data Center Plugin in v8.20.10

I am trying to start work on a custom Jira Plugin for our team. I was following the instructions on this page to get started creating and realized the SDK it’s asking me to download Isn’t compatible with our Version of Jira. I put in a support ticket and was told to look at AMPS and Maven for plugin development. Could I get pointed to some resources similar to the page I’ve linked above that refer to plug in development with AMPS and or Maven? We are using Jira v8.20.10. Thank you.