In React Native, you can use map or flatList for rendering an array. If you are trying to display a large amount of data it is better to use flatList(better performance with large amount of data).

Replace this code

  {tickets.map((ticket) => (
    <Text key={ticket.id}>{ticket.form.TicketNumber}</Text>
  ))}

with this code

<FlatList
data={tickets}
renderItem={({item}) => <Text>{item.form.TicketNumber}</Text>}
/>

Try this may be your state is getting set before your data is pushed in array put it outside loop like this

const [tickets, setTickets] = useState([]);

useEffect(() => {
    GetTickets();
  }, []);

  console.log(tickets);


  const db = getFirestore();

  const colRef = collection(db, "Tickets");

  function GetTickets() {
    getDocs(colRef).then((snapshot) => {
      let tickets = [];
      snapshot.docs.forEach((doc) => {
        tickets.push({ ...doc.data(), id: doc.id });
      });
      setTickets(tickets);
    });
  }

  return (
    <View style={GlobalStyles.container}>
      <Text>Previous tickets</Text>
      {tickets.map((ticket) => (
        <Text key={ticket.id}>{ticket.form.TicketNumber}</Text>
      ))}
    </View>
  );

I'm not sure if it will help you but 2 comments for help you in your search:

• You are calling setTickets inside the loop, smells like a problem, because of the async flow.
• Also, why are you defining the variable name in the scope of the function, with the same name of the variable for state of the tickets, smells not so good.

Hope it can help you.