Not open source, but https://financier.io/ is browser-based YNAB clone. I'm still using YNAB4 for the time being, but will probably switch to Financier once YNAB4 stops working.

EDIT: Looks like it's been updated to be an open source project: https://blog.financier.io/financier-is-now-open-source-bdfe9...

Financier looked absolutely great when I tested it a few months ago. But: lot of features missing (like recurring transactions) and the app seems to be abandoned. At least there was no activity for over a year now. What a pity.

IIRC, it's not so much abandoned as in what the author considers a finished state. I still use it and actually just paid another year's subscription.

Like you say, there are some missing features, but it does what I need it to perfectly.

There's a google sheet floating around reddit that's pretty much a YNAB clone. I just use an excel spreadsheet thats formatted to take a copy paste from my bank/cc .csv transaction list, then I go through and categorize the transactions for the past month. Takes 10 mins or so.

I used to use mint which was more automatic, but things rarely get categorized correctly, and by doing it by hand, I'm a lot more aware of my spending habits than if I just looked at some pie charts. I can still make pretty charts in excel if I ever wanted too.

That was my idea behind https://github.com/seveneightn9ne/dino-budgeter - you can try it out at https://dino.jesskenney.com/ - it's missing a lot of the sort of guidance/hand-holding that YNAB provides, and so far it only has the features I personally wanted, but it's at least been enough for me :)

Author of My Budget.

I'm taking inspiration from YNAB, as it has a rich feature set. Also open source so that's a plus! Thanks!