I found an 18+ vanilla Minecraft SMP running on 1.21.11. It feels relaxed and made for adults who want normal survival without a bunch of extra stuff.
PvP can be turned on if you want it and it is allowed. Griefing and cheating are not allowed so people can actually build and chill.
There are some quality of life features and only minimal plugins. They have warps a shopping district and in game voice chat. It usually has about 5 to 15 active players each day and the community is tight knit and welcoming so it is easy to fit in.
They also make YouTube content and sometimes do scripted events and storylines. It is good if you want to be part of something bigger while still just playing survival.
