This is more of a cross-compatibility issue with other mods' enchantments I presume, but after feeding the Hunger several different enchantments (which are all able to be combined on an anvil, I checked), it refuses to enchant any book fed. It doesn't simply reject the enchanted items; it eats them, then it won't spit anything out again. It won't eat anything else either, leaving it useless.

Example: Giving it Dash (from Dash) and Shockwave (from Allurement), which can both be combined on an anvil, then feeding it a book, it'll spit the un-enchanted book back while storing everything else. It'll still eat any enchanted object it's compatible with like regular Unbreaking, but it just ends up in a state of not being hungry (lol) anymore.

Minecraft 1.16.5
Forge 36.2.22
Mod Version 1.2.4

Once again I'm not sure if it's a bug or a feature. It's just an inconvenience, and something that's probably more trial-and-error testing and other things.

Never mind, I guess I didn't read the config where you can set the amount of enchantments stored. I changed that number, and now everything is fine and dandy again.