Lots of other great answers, another one I came across recently is FinGPT[0]. For backtesting there is zipline [1], but doesn't look like it's maintained anymore.

[0] FinGPT: Open-Source Financial Large Language Models https://github.com/AI4Finance-Foundation/FinGPT

[1] Zipline is a Pythonic algorithmic trading library https://github.com/quantopian/zipline