MARTA Q from a visitor

Hi all, European visitor here, in Atlanta this week for a conference and slowly losing my mind trying to work out how to use public transit. For the record, I’m not judging, I know that MARTA is going through some kind of fare system upgrade which is causing all the disruptions, and Atlanta actually seems to have the best public transit system of all the American cities I’ve visited so far. I only wish the city was better at communicating how one should go about purchasing fares. I tried to use the streetcar today (and will have to do it again later this week), I couldn’t buy a fare at the stop because the vending machine was out of service (I’m guessing this is related to the system changes). Then I tried to buy a fare inside the streetcar, I didn’t have exact change so I just used a $5 bill but didn’t receive a physical ticket/receipt. Is that normal? What happens if there’s a ticket inspector onboard? Do they just take your word for it that you did pay?

And the trains. The tap-and-go fare system worked at only one station I’ve been at so far. From what I understand, when the gates are left open and there’s no way to pay, you can just enter without a ticket. But, again, what if there’s a ticket inspector? I tried using the Breeze Mobile 2 app and it says “There are no available items in the list” when I try to buy a fare.

I'm taking the bus for the first time tomorrow. Any recommendations on how to buy a fare?