Here is the first Release Candidate for 1.21, addressing some critical issues. Apart from that we decided to revert the changes made in Pre-Release 4 to armor enchantments based on your feedback.

Happy mining!

Changes

• The changes to Burn Time reduction from Fire Protection and Knockback reduction from Blast Protection from pre-release 4 have been reverted
  • We have heard your feedback, and we expect to rebalance these two enchantments in the future to find a better place for them
  • Values are now the same as in 1.20.6
  • These effects still stack from wearing multiple pieces (changed from 1.20.6)

Fixed bugs in 1.21 Release Candidate 1

• MC-272888 Zooming with riptide still applies mace wind burst if held in main hand
• MC-273007 Projectiles have incorrect motion when shot from a vehicle which was entered with player velocity
• MC-273158 Animals stay floating after getting on a boat