What insect is identified by long snouts and dark forewings that cannot fly found within a mill?

The identification of the insect with long snouts and dark forewings that cannot fly corresponds to the granary weevil. This insect is a common pest found in stored grains and is actually flightless, which aligns with the description provided in the question. Granary weevils are known for their distinctive elongated snouts, which they use to bore into grains to lay their eggs.

In contrast, cereal moths and rice weevils have different physical traits and behaviors, such as flying capabilities. Carpet beetles are also quite distinct, belonging to a different family of insects altogether and lacking the prominent snout characteristic of weevils. This highlights why the granary weevil is the accurate choice, given the unique features described.