I found Iperios and it is a modded server where players can make their own nation and run it how they want. You can pick a form of government and set laws and ranks for your group.
If you do not want to start from scratch you can also join a nation that already exists. It feels like a mix of survival and roleplay where the community decides how things work.
The server uses the All the Mods 10 modpack and it says version 5.5. To get in you join the Discord and ask for whitelist then a staff member helps you and gives you a beginner kit.
WebsiteDiscord