I can only use the normal elytra in the armor slot but not in the cape slot. And the Elytras from the better end mod don't work completely. That only happens when the origins mod is installed

This behavior should be fixed by Origins migrating to use FabricMC/fabric#1815 to implement its elytra flight.

Made a new issue to represent the migration, which can be found here: #465

No longer relevant since Origins uses the new Fabric API starting in 1.2.0.