I found a brand new adults only Minecraft server that is made for people 18 and up who still like to play in their free time.
It is pure vanilla and it runs on 1.21.11. The community is small right now and they want more players to join and hang out.
It is whitelisted so you have to apply before you can get in. They also ask you to be patient since it takes a bit to get approved. The whole point is a friendly place without kids bothering anyone.
