Another option in this space is Tiller (https://www.tillerhq.com/). They seem well-established, and offer some spreadsheet templates for plug-and-play solutions to some common budgeting scenarios.
If you don't care about spreadsheets specifically -- if you're just looking for scriptable access to your financials -- Lunch Money (https://lunchmoney.app) has a public API. They'll also be opening the beta of rollover budgeting any day now, which has me excited!