I found a server called Warshipcraft and it runs on Java 1.21.x with Paper. It also has a Bedrock port so more people can join in.
It has a lot of plugins like a ridiculous amount. The developer is active and the owner has been running it for years since 2017 so it feels like it is not going to disappear.
The server is kind of niche and it is focused on warships and guns on an Earth style setup. The staff are older people and they try not to use admin powers in the main world unless it is really needed.
