Upgraded from paper 1.15.2 to 1.16.1 this morning.
I have a bukkit.yml within a line saying: world-container: worlds
This means I can put my world files together in a folder away from the server configs.
However starting the latest dev build of paper 21 its generated new world files in the server root folder.
Spigot removed this due to some issues around load order, you now need to specify it at startup
-W, --universe, --world-container, -- World container (default: .)
world-dir <File: Directory
containing worlds>
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Spigot removed this due to some issues around load order, you now need to specify it at startup