Install the universal flipper build tool with pip:

pip3 install -r requirements.txt

Update the build tool:

ufbt update

Create the app project:

ufbt create APPID=matrix_ss

(Organizing everything under src/ because the .c and manifest files need to be kept separate from the readme, virtual environment, and other files.)

Build the app:

ufbt

Launch the app on the flipper:

ufbt launch