Are All the Items the Same?
Trivial Built-in Answers
This is the post for all of the languages where this is a built-in
Vyxal, 1 byte
≈

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Jelly, 1 byte
E

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05AB1E (legacy), 1 byte
Ë

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Wolfram Language (Mathematica), 5 bytes
Equal

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SameQ also works.
Brachylog, 1 byte
=

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Husk, 1 byte
E

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Factor, 3 bytes
std

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Outputs 0.0 if they're the same, or something else if not. all-eq? and all-equal? are longer built-ins that output booleans. all-equal? uses = (ordinary equality) and all-eq? uses eq? (strict object reference equality), but they behave the same for integers.