Learn Spanish (Latin America): ¿El documental está en esta plataforma?

They look similar but do very different jobs. está (with an accent) is the verb meaning is, from estar. esta (without an accent) means this, pointing to the feminine noun plataforma. The accent mark changes both the meaning and which syllable gets stressed when you speak.

Why do we use está instead of es for a digital platform?

Even though a digital streaming service is not a physical place, you are still talking about the location of the documentary. Spanish uses the verb estar whenever you are talking about where something is located.

Is there a rule for the gender of words ending in -al like documental?

Most Spanish words ending in -al are masculine, which is why we use el documental. Just watch out for a few common feminine exceptions like la capital (the capital city) or la señal (the signal).