We have a large and old world that generated in version <1.8. We won't wipe it during version updates (and this world has already experienced ~10 major updates), as we need to keep players buildings. So, this is a long story..

In general, next update 1.18 will bring us a feature called "biome blending", we're very like it and and thanks to it, we planned to extend the world twice. BUT we want to keep the current chunks "as is" and bedrock level inside it at y=0. Currently there is no way to do this :c

We will be very grateful if you add something like disable-new-chunks-under-existing-chunks to spigot.yml.