Per world seed?

[turbid oar]

What would that supposed to be?

[sacred lake]

I have it as a feature in a private mod. What do you need it for? If you want to prevent reverse seed engineering I can also recommend you my https://modrinth.com/mod/seedguard mod

sure! It's just one super simple mixin:

@Mixin(ServerLevel.class)
public class ServerLevelMixin {
    /**
     * @author Drex
     * @reason Implement per world seeds, fail fast
     */
    @Overwrite
    public long getSeed() {
        // TODO: Get worldSeed (from config etc)
        // return worldSeed;
    }
}