For normal players:

• 1.21.5: Added leaf litter, wildflowers, cactus flowers, bushes, firefly bushes, and dry grass.
  • Added 3 new wildflower colors, in addition to the vanilla yellow/white ones.
• Fixed pale netherrack textures in old MC versions. Again.
• LOD rendering now has fog.
  • Density parameters are configurable.
• Possibly fixed LOD renderer causing crash on some hardware/OS/JVM combinations.

For data pack developers:

• Ores (and possibly other things that map blocks to other blocks) can now use tags for the block to map from.
• Fixed being unable to use wood palettes in overriders.
• Added nullable casting syntax: Type?(expression) casts expression to Type, or evaluates to null if the expression cannot be cast.
• Improved error reporting when failing to compile column values.
• Possibly fixed issue with syncing booleans to the client for constant column values/decision trees/etc...