This datapack does one small thing. It lets you decide what item should be in the end ships item frame.

Simply go to the file under elootra.zip\data\server26elootra\functions\check_frame.mcfunction and locate the line starting with "execute as..." you will find a text saying "minecraft:nether_star" (this is the default item that will replace the elytra) just edit this text to any minecraft item you wish. If you have mods this should even accept modded item names.

Disclaimer!!! This will replace all elytras in item frames prior in the world (even the ones in your base for example). Elytra placed in frames AFTER the pack has been enabled will be fine, but not the ones before, so be aware.

"I want NO ITEM to spawn in the frames":

replace the "execute as.. line in the check_frame file mentioned earlier with this one. Yes, the disclaimer is also hold for this one.
execute as @e[type=minecraft:item_frame,tag=!elo_tagged,nbt={Item:{id:"minecraft:elytra"}}] run data remove entity @s Item.id

Edit: This pack does not contain any loot tables per se but is listed as such since the "loot" is still edited