I tested this in mushroom biome with sheep, chickens, pigs, and mooshrooms. Of those, only the cows spawned, the sheep, chickens and pigs did not. Hostile mob spawners work as expected.

I'm running Fabric under 1.18.1 and the mod with the latest versions at the time of reporting. Thanks.

This mod does not alter the spawning rules of the spawner. The vanilla rules only allow certain mobs to spawn in certain biomes.

@andersblomqvist can you or would you maybe add a config option to "Ignore"/"Overwrite" such spawning rules?
Would be really cool if so :)