I found a chill vanilla survival SMP that is whitelisted and meant for a small community. It has a relaxed casual vibe where people can build explore and just hang out.
There are only light rules and the big one is do not grief builds. PvP is allowed so fights are fair game. They also have some tiny qol plugins but it still feels like vanilla.
The world border is set to 10k for now and all ages are welcome. The server is located in Germany and they may add new features later if the community wants it.
