I found a small and friendly SMP called the Underground SMP. It is a Java server on 1.21.11 and it is all about living under a giant bedrock wall.
Everyone starts trapped underground and you get to pick one of four kingdoms or areas to begin in. The server runs events where players can unlock certain items that are up above the bedrock wall.
The community is open to all people and they also want content creators to join in too. It sounds like a chill place to meet others and take on the underground challenge together.
