Not affiliated in any way with Actual Budget, but I can’t recommend it enough. It’s the FOSS version of YNAB pretty much so if you’re a fan of envelope budgeting it’s a great tool. I’d even say it has quite a few other strengths compared to YNAB, and you can always be sure that your financial data stays within your reach.
That’s alright. Even read-only access is useful. I could write a script that pulls my current investments, prompts for the amount I’ll be investing in total, and prints out the buys (eg “buy 10 x VOO, 5 x VXF, 20 x VXUS”) that’ll keep the account balanced based on some percentages.