You don't want to know! You could hook up an API using Plaid. At the personal level the cost should be minimal. If all your accounts are supported.

(I use placeholders with schedules to ease my burden, but ultimately I track every transaction manually.)

I use YNAB4 through wine and wrote a little CLI utility to ingest CSV statements and format them to what YNAB expects (with currency conversion at the transactions rate for that day). It works well and is all local.