ViaVersion

1.21.4 client support and mostly config-related changes and fixes to older server versions!

• Greatly reduced netty byte buf (memory) allocation
• The sword-blocking emulation for 1.20.5+ clients on 1.8 servers can now be disabled via sword-blocking-via-consumable (by EnZaXD)
• The fix-1_21-placement-rotation config option is now enabled by default (by Pro4D)
• Fixed reading of equippable (by DavyCraft648)
• Fixed reading of armor trim override materials
• Fixed regression in tag sending for 1.20.2 to 1.20.4 clients on older servers
• Fixed recipe book recipe ingredients for newer clients on 1.12 servers and older (by valaphee)
• Fixed block action block id handling across multiple protocols (by valaphee)
• Fixed 1.12->1.13 block connections on snowy grass, mycelium and podzol (by lowercasebtw)
• Fixed dropped items being invisible until entity data is sent in 1.10->1.11 (by EnZaXD)
• Improved 1.21 client enchantment handling on legacy servers (by Pablete1234)
• Fixed fix-1_21-placement-rotation not working after changing its value and running /viaversion reload (by EnZaXD)
• Fixed fix-1_21-placement-rotation causing some issues with with anti-cheats (by EnZaXD)

Additional notes:

• Custom model data no longer exists in its previous form. If you can, use the item_model data component, else make sure your resource pack is updated to use the new custom model data format and its first range_dispatch float
• Picking blocks will not work for 1.21.4 clients on servers older than about 1.12. Picking entities does not work on servers older than 1.20.4. Both are Paper specific platform fixes and require certain API to be present

If you want to get larger version updates early, consider supporting me via https://viaversion.com/donate. See the previous update notes for more info.