Worst case scenario, call support to put a credit card on file with your account. This is what I did when I ran into problems with the app (turns out I was too eager trying to use it before they were done setting me up).

When you use a supercharger, at least as a Tesla, there is a handshake where your car identifies what account to use, then it just works

You definitely lose a lot of convenience features if you don’t use the app, but I believe you can do it, if you want it enough

Edit: just use a web browser. I verified I can login through my web browser to manage my account, my products, my payment method. Not the car features though. I have no idea if this is new, but just use any web browser