Minecraft wiki entry for Development_versions, associated text: Can now disable lightning flashes, which prevents lightning from making the sky flash. Lightning bolts themselves will still appear.
The device the game outputs audio to can now be chosen in-game.
Added "Priority updates" to video settings.
Determines as to which chunk sections are updated synchronously in a single frame.
Three options:
nearby, which corresponds to how chunk sections were updated before 21w37a, and by player and none, which reduce stuttering when placing or removing blocks.
However, the latter two options may cause rare visual delays in world updates. These options also appear to be improperly capitalized.[21]