In Brazil there is a very successful cash alternative called PIX. My personal problem with it is that I still can't find a single FLOSS app to use it. For now,

In Brazil there is a very successful cash alternative called PIX. My personal problem with it is that I still can't find a single FLOSS app to use it. For now, I have to resort to cash or cards. For people who don't want to depend on proprietary software to make payments, what are the current trends and alternatives?