A self-hosted version of YNAB. It's a subscription based budgeting service. It's truly a fantastic service that helped me a lot, but their prices have skyrocketed. I tried getting into plaintextaccounting/double-entry bookkeeping using ledger or beancount/fava, but it's just not as nice as YNAB.

I feel a really solid self-hosted personal budgeting service would be fantastic, based on plaintextaccounting/double-entry bookkeeping which is a very open standard and really easy to deal with.