I remembered that you can request an app directly in ‘Apps’. What happens after that I have no idea but I see another post where someone asks the question.
Someone has raised an issue on gitlab requesting some sort of tracking for user requests.
Also, in the editable list of apps that do or don’t work on eOS Argenta is listed as working, but payconiq listed as not working (it may not be exactly the same as the app you need though). Anyway it’s always worth trying on your own device to make sure.