A client-side fabric (quilt-compatible) mod which allows you to lock elytra functionality.
It registers a keybind (by default, J) which can be used to toggle the lock.
When locked, it is impossible to fly or equip the elytra with right-click - it is possible to equip to it manually, by shift-clicking or dragging it onto the chestplate slot. If the elytra is locked when it is already equipped or equipped manually, flight is disabled.