River is meant to work with Python 3.8 and above. Installation can be done via
pip install river
You can install the latest development version from GitHub, as so:
pip install git+https://github.com/online-ml/river --upgrade
Or, through SSH:
pip install git+ssh://firstname.lastname@example.org/online-ml/river.git --upgrade
Feel welcome to open an issue on GitHub if you are having any trouble.