KMyMoney is what I use. (Though I haven’t kept it up to date for way too long)

Depends what you use it for. I’ve only used QB-like software for basic checkbook management.

Someone already mentioned GNUCash, so there’s definitely that.

I switched a while back to a webapp I run called FireflyIII. The only thing I don’t like about it is that the import tool (to import transaction records from my bank) is a separate webapp that’s a little clunky to work with.

Not sure if that’s changed recently (I really need to update lol), but you can still enter everything manually through the web UI.

Personally I like and have been using beancount with my own instance of fava. It’s text based and may take a bit of getting used to coming from quickbooks, though.