Learn Turkish: Liste komitece hazırlandı. - The list was prepared by the committee.

The suffix -ce (which can also be -ca, -çe, or -ça depending on vowel harmony and consonant mutation) is attached directly to the agent in a formal passive sentence to mean 'by'. Since komite ends with the front vowel e, it takes the -ce form.

Could I use tarafından here instead of the -ce suffix?

Yes, absolutely! You could say komite tarafından and it would mean the exact same thing. The -ce suffix is just a shorter, slightly more formal alternative to tarafından, and it is especially common when the agent is an official group, board, or organization like a committee.

Why is the passive suffix in hazırlandı just -n? I thought passive verbs usually took -ıl or -ın.

You are right that -ıl and -ın are the most common passive suffixes. However, as a quick refresher: when a verb root ends in a vowel, like hazırla- (to prepare), the passive suffix is simply -n. So, hazırla- plus -n plus the past tense -dı gives us hazırlandı (was prepared).

Shouldn't liste have the accusative case suffix (listeyi) since it is the specific thing being prepared?