I am using flutter for frontend. I want to make a financial application.

• Application will read data from web APIs
• Application will make calculation for candlestick datas. For example user will select pair and program will analyse it. It will tell support and resistance levels.
• I know python libraries and c# libraries for making technical analysis.
• If I can do the backend operation in phone it is better for me. I do not want to own a server.
• I tried using .py files with flutter. I tried startflut but their support is no longer anymore. I looked in into flutnet but it says I should create a xamarin first.
  Which backend should I use I I want to make financial application ? And which path should I follow ?