Press f3
Observe the current biome
Descend to y=-60 in 21w06a
Once you are below the bedrock, no biome is listed
Running /locatebiome minecraft:the_void returns no result
Damage is delt as expected in survival.
Affects all dimensions.
While testing discovered MC-214790
Comments 2
The biome "the_void" is only for custom worlds / flatland worlds. https://minecraft.gamepedia.com/The_Void
There are no biomes outside of the world's limits.