In the latest snapshot (24w33a) that was released recently there was a bug in the enchanting table. When you try to enchant a part of your armor in the enchanting table it doesn't work, which shouldn't happen because in the latest version (1.21.1) you can enchant a part of your armor without problems in the enchanting table. Regarding the tools, they work correctly.
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is duplicated by 3
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Can confirm that it affects both vanilla items and custom items with the 'enchantable' component (in the goat horn picture's case, I even added enchantable tags to the goat horn in a data pack).
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It seems like armor is missing the enchantable component entirely, as removing the component from the item does not reduce the component count. Adding the component manually through commands, e.g.
/give @s diamond_helmet[minecraft:enchantable={value:1}]seems to allow the armor to be enchanted through the enchanting table again.
Can confirm:
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