I found this SMP that keeps it super simple. It is basically vanilla with only minimal add ons and the main rule is do not cheat.
It has simple voice chat so people can talk in game. The Nether and the End are open and it is kind of a race since anyone can go if they get there first.
String duping and TNT and sand duping are allowed. It feels like classic survival where you just do your own thing but you should still watch your back because someone could be watching you.
One Rule Vanilla SMP No Cheating
GG.MINEWIND.NET New Server IPPlayblocks Earth Map and Nether Exploration Minecraft Server
Playblocks is a Minecraft server featuring an exploration friendly world with access to multiple dimensions. The Nether has been fully opened so players can explore and build in that dangerous realm. The server includes a 1 to 500 scale Earth map where you can start your town near where you live in real life. Players can also use public portals to travel to the End and Nether, making it easy to move between dimensions. You can vote for the server using in game commands to receive keys that unlock various rewards. There are additional features beyond these core systems that aim to keep gameplay engaging for everyone.
GG.MINEWIND.NET New Server IP