Their explanation as to why:
--no-quarantineis used to forcibly bypass Gatekeeper, which is a built-in macOS security mechanism. This is used to run unsigned/unnotarized applications.macOS Tahoe is the final release to support Intel systems, and last year Apple updated macOS runtime protection to make it harder to override Gatekeeper. Macs with Apple silicon also don't "permit native arm64 code to execute unless a valid signature is attached". Finally, we are ending support for all casks that fail Gatekeeper checks on September 1st, 2026.
With the above in mind, it's time to deprecate the
--no-quarantineflag frombrew. It intentionally bypasses macOS security mechanisms, which we already actively discourage. Deprecating now will give a decent lead time for users using it to come up with another solution or adjust their workflows.
Apps have to be signed to be installed.