This is a very simple plugin that allows you to combine an elytra with a diamond chest plate in an anvil.
The result will be an armored elytra.
Armored elytras offer the same amount of protection as a diamond chest plate and they can have the same enchantments as well. This means that you can add protection, fire protection etc to the armored elytra as well.
By default, you can only see the elytra when a player wears an armored elytra. However, you will be able to see both the armor and the elytra at the same time if you install THIS Fabric mod on the client!