I personally use a spreadsheet. I never found an "app" that was simple enough to use and didnt bombard me with ads or use my data.

Its easy enough and I am able to customize it as needed etc. Mine is as simple as Columns across the top for account balances, and essentially a ledger of payment activity for my checking account that I use to pay my bills. As I enter, it adjusts the balance, and further down are my budget amounts/sunk cost funds that I offset based upon actuals. I use a credit card for all purchases and as soon as transactions post, I make payments and track them in the ledger with offsets to the budget accounts. Clean, simple and I know where every single cents goes.