My ideal setup would be YNAB, I really liked that program but unfortunately their current price is too high for me. So my plan for now would be to use beancount as normal (possibly with a telegram bot for entry + imports every week or so, with deduplication), as beancount has good existing tooling and is more strict than (h)ledger, and writing a frontend for budgeting on top, as that is not strictly part of the ledger itself. So that frontend would just make a weekly balance of expense accounts, and each could be mapped to a budget.