You can setup your own if you wish, but a lot of these parties also have had an audit done on security and on privacy. That is not gonna matter if you live in the US, but that is a problem

I have had a lot of issues setting up Firefly III on different systems so I never got to get it working.

Eventueel I ended upfinding Actual Budget, while not perfect it works really well and I have been using it for more than a year now

Actual Budget a selfhosting budget software. It helps me keep track of my finances