I know, there are a lot of tickets/topics for this feature, but Forge has added the support for custom elytra (ok, we need to have Forge for 1.16.1). So, as I know that a lot of users want this feature, I create a ticket. I have only the link of the commit on GitHub, but I don't know if it can help. https://github.com/MinecraftForge/MinecraftForge/commit/399bc6c9c34e930…
Issue comments
Just for the reference for people wanting to code it: https://github.com/MinecraftForge/MinecraftForge/blob/1.16.x/src/test/java/net/minecraftforge/debug/item/CustomElytraTest.java
I know this. Please leave a comment here so I can repoen when 1.16.x is fully supported, as stated, I don't want a flood of tickets that are out of scope atm.