A "Plaid" style solution is needed for EV charging
" First and most significant is that I neither live in Europe nor am I an EV owner. It's entirely possible this problem is localized to Scandinavia because of how mature it is, and that’s not obvious to me. "
Absolutely not. I live in N. California & have a non -Tesla EV and the same thing is true. I have about 5 different apps on the phone and there are other chargers around. Impossible to tell if they are used or empty or working or not in most cases, and yes, you cannot just show up with a credit card and tap. It should be like the London Transport network which now allows you to tap a credit card on or off any tube, bus or train AND it figures out your best fare over the day or week (i.e. if you'd been better off buying a weekly ticket, it gives you that price). Why the different charging companies can't let you tap a credit card when any tiny store anywhere in the world does is beyond me...
Talk to the team at Smartcar (https://smartcar.com/)!
You need eRoaming to interconnect all EV charging networks not one app for all. This is a competitive market that can be compared with the banking or cellular roaming. There are many banks around the world and thankfully you can now use one Debit card to get money around the world. This is what eRoaming allowed not "one app" which is not even integrated with most international networks. Here is how it is possible to interconnect 300'000 charging point in Europe and the same is happening in the US: https://saascharge.com/what-is-a-public-ev-charging-network-and-how-does-it-work/