I created this little plugin for my server but decided to share it on modrinth.

Feature

• Remove Elytra from END's worlds.
• Configurable min/max Y level.
• Configurable whether to check for elytras in all item frames in The End (not just in ships with boats).
• Configurable alternatives:
  • REMOVE_ELYTRA
  • REMOVE_FRAME
  • REPLACE_WITH_APPLE
• Configurable messages.

Version

The ElytraRemover plugin works on my paper server 1.21.4 build 226#. Not tested anything else.

Example config.yml

# ElytraRemover Configuration File

# Check interval in seconds (how often to scan for elytras in item frames in End ships)
check-interval: 10

# Debug mode (enables additional logging)
debug: false

# End ship detection settings
end-ship:
  # Minimum Y level for end ships (used for detection)
  min-y: 0
  
  # Maximum Y level for end ships (used for detection)
  max-y: 256
  
  # Whether to check for elytras in all item frames in The End (not just in ships with boats)
  remove-all-end-elytras: true
  
  # How aggressively to scan chunks (higher = more thorough but more resource intensive)
  # 0 = basic, 1 = normal, 2 = aggressive
  scan-intensity: 3
  
  # Action to take when finding an elytra in an item frame
  # Options: REMOVE_ELYTRA, REMOVE_FRAME, REPLACE_WITH_APPLE
  action: REPLACE_WITH_APPLE

# Messages
messages:
  # Message logged when an elytra is removed from an item frame
  removed: "Removed an elytra from an item frame at location: {location}"
  
  # Message logged when a player tries to place an elytra in an item frame in The End
  prevented: "Prevented {player} from placing an elytra in an item frame in The End"
  
  # Message shown to players when they try to place an elytra in The End
  player-notify: "§cElytras cannot be placed in item frames in The End."