Learn Portuguese (Portugal): A homenageada, cineasta e produtora, discursou. - The honoree, filmmaker and producer, gave a speech.

This phrase is an apposition—a noun phrase placed between commas next to another noun (a homenageada) to describe it. In Portuguese, you usually omit the definite or indefinite article in an apposition when it states a person's profession, title, or status.

How do we know if cineasta is feminine here, since the word always ends in "-a"?

Cineasta is an invariable noun for professions, meaning it is the same for both men and women (o cineasta, a cineasta). We know it refers to a woman in this sentence because it describes a homenageada (the female honoree) and is paired with produtora, which is the explicitly feminine form of produtor.

Homenageada looks like a verb form. How does it work as a noun here?

It is the past participle of the verb homenagear (to honor). You can easily turn Portuguese past participles and adjectives into nouns just by adding a definite article like o or a before them. Here, a homenageada literally means "the honored woman" or "the honoree".

Could I translate "gave a speech" literally as "deu um discurso" instead of using discursou?

You can say fez um discurso or deu um discurso, but Portuguese often prefers using a dedicated single verb when one exists. Using discursar sounds more natural, concise, and elegant, which perfectly fits the formal tone of honoring a filmmaker.