A while ago I built a simple SMS bot for my partner and I to track finances like this, and it works fairly well. The workflow is whenever we spend money we text it with "spend <amount>" or "sp <amount>", and whenever we receive money we do "add <amount>", and "save <amount>" whenever we move money to savings.

I added some minimal polish like an undo command, a minimal GUI accessible via a short-lived link it sends us on request where we can add and edit recurring bills, subscriptions, and upcoming one-time or yearly major expenses. It has support for debts/loans (we can do "cc <debt> <amount>" for increasing debt, e.g. by paying with a credit card, and "pay <debt> <amount>" for payments). It sends us nightly and weekly reports letting us know progress towards savings goals and warning us if we're about to run into a tight spot based on what it knows about our spend rate, and upcoming bills and big expenses. It also bugs us if it notices we haven't transferred anything to savings recently.

The fact that it doesn't sync automatically with our bank accounts is actually a feature, because the ritual of having to text it whenever we spend money forces some mindfulness of our spending habits, and the regular reports (where it chides us if we're not saving much or exceeding our spending goals) add some gamification -- we joke about how we want to make it proud of us. :)