Learn Portuguese (Portugal): A praia está longe.

In Portuguese, the verb ser is used for permanent characteristics, but estar is used for locations. When you talk about where a physical place or object is located, you generally use estar, even if that place never moves.

Could I use the verb ficar instead of está in this sentence?

Yes, definitely! For permanent locations like buildings, cities, or beaches, European Portuguese speakers very often use the verb ficar (which literally means to stay) to mean is located. You will frequently hear the phrase A praia fica longe.

Since praia is a feminine noun, does longe need to change to match it?

No, longe is an adverb meaning far or far away. Because it describes the distance and not the noun itself, it does not have a masculine or feminine form. It never changes to match the noun, so it will always be exactly longe.