Assuming you mean "free" as in "I don't need to provide a credit card to sign up", then https://ghostfol.io/
If on the off chance you mean "free" as in "freedom from having my data sold", then You Need a Budget (YNAB) is a popular option. But be warned, YNAB is more than software...it's a new way of thinking about budgeting. It takes some getting used to.
https://www.ynab.com/
I have so many of these self-hosted apps in my server now, it's getting rather full but it's so freeing to know my cloud is just mine. My data stays on my machine and isn't reliant on some server farm christ-knows-where, their infrastructure, and their security policies which are all effectively required to be taken on faith.
I absolutely love it and I have so much appreciation for the people building this stuff.
Care to share some useful apps you have been using? I recently got a NAS and found out it's quite easy to host a service via docker and forward connections with cloudflared.
So far I am running vaultwarden and an audiobook server using plex.
Either it's accurate so nobody uses it so I don't have confidence in it, or the number is wrong but nobody's noticed this glaring error on the home page and so I also don't have confidence in it...
I use Fidelity Fullview(must be a customer of Fidelity but that can also be free). Fidelity also has eMoney, which is a more comprehensive option, but requires going through a financial advisor that supports it.
Otherwise the other options people have mentioned are decent, particularly hledger.
Not that you should trust that your info is any safer than with Mint, but has anyone tried Personal Capital? I've seen it recommended in the past, but they seem to have rebranded and their site doesn't list much detail about it. https://www.personalcapital.com/
I use personal capital and it's just about the same as mint, with a more "investment" focused tooling set as they want you to buy their fund.
Beyond that, a few CC providers have terms that say "you aren't protected if you give out your password to services like this" so do keep that in mind (I didn't wire up some accounts explicitly for that reason, and I track them manually in the tool)
Wish the US would get it's act together and mandate a modern open banking API.
I got tired of the pushy sales calls for their managed option. Kind of turned me off. I wish I could have just paid for it. I eventually switched to tiller ($5/mo) as it mostly works and is super configurable (just a spreadsheet synced with bank data)