air travel – Losing connecting flights when transferring between airports

If you fly on one ticket, as you said you do, you will be booked on the first available flight if you miss your connection, assuming you have done your best to get there in time.

Best contact the airline (one of the cabin crew will do) before landing how to handle the transfer, so you know what is the recommended way to handle the transfer.
Check whether you need to pick up your luggage (which is likely) and take it yourself.

Some airlines have special shuttles between different airports when they have many passengers that need to make the transfer. Most do not but they might tell you to use one shuttle company or one connection method which is more reliable or faster than the others.

And when you arrive at your next airport, there might be ways to get you through the system faster if you report in the right way to the right place. That is an other reason why you should ask before you leave the first airport, likely the cabin crew will know it.

The last good time to ask the cabin crew is well before landing, even before the last food service before landing, as they are often rather busy in that last period. It would not hurt to mention it when you are waiting to board the flight if the ground staff is of your airline and not from the airport, and again as soon as the first food service in the flight is done, so the crew can come back to you when they have time, and can even ask for the information if they do not have it yet.

If you get no (good) answer from the cabin crew, ask ground staff in your arrival airport. Do not leave the airport without the advice, as not following it might lead to the airline denying you your next leg of the journey if you do miss the flight.