You can simulate various forms of envelope budgeting in Ledger (aka. ledger-cli) and the similar projects like hledger. There are quite a few of blog/forum post

You can simulate various forms of envelope budgeting in Ledger (aka. ledger-cli) and the similar projects like hledger. There are quite a few of blog/forum posts out there that help explain how to do this. If you're specifically looking to emulate YNAB, there are also some posts that deal specifically with this.