That's true. The users have a high motivation and a lack of resources, so they wouldn't worry about app size or installing the app. However, the UI has to be friendly and non-fatiguing. As you said, I will focus on the frontend now and use firebase to avoid complications in the backend.

I just have one concern though, the user will be interacting heavily with the flashcards while studing and I want to store that info for the algo. Should i go with an on-device database for it? or Firestore can handle it?