I found a survival server running on 1.21.10 and it feels like a mostly vanilla SMP with a clean setup.
The big twist is custom structures placed around the world so exploring does not get boring and you can stumble into cool stuff while roaming.
It also supports joining from multiple Minecraft versions because it uses ViaVersion and ViaBackwards so you do not have to be exactly on 1.21.10.
The community is small and still growing and the whole place is meant for building exploring or just chilling without feeling like another number. Performance is also said to be stable.
Vanilla Survival SMP With Custom Structures
GG.MINEWIND.NET New Server IPSimple Survival SMP Launching Feb 20
I found a normal SMP that is trying to keep things simple. It is not modded and it has no economy so it feels like classic survival.
There are only a few plugins and they are meant to not change gameplay much. The world is planned to have no resets so you can build and keep your stuff long term.
It also supports crossplay so more people can join together. The server is launching on Feb 20 and they want you to dm or comment if you want in.GG.MINEWIND.NET New Server IPMedieval Vanilla Launch With Small Community
This is a medieval style vanilla server with a small community around 10 players right now.
The server has not started yet so everyone can jump in at the beginning. It is planned to start in about 3 days maybe sooner.
It runs on Java 1.21.11. If you have questions you are supposed to ask the admin in their Discord.GG.MINEWIND.NET New Server IP