Which type of applications? What I have found to be finicky is the desktop environments, however BSDs are pretty much tuned for web servers/applications. Bastille is designed for deploying web applications in jails securely and built on top of FreeBSD which is a pretty good default OS that gets out of your way already.
Normally you don't release an app for BSD specifically unless you want to offer a port. In which case software is usually built and if you need containerization you can put it in a jail.
It seems you would do well to install a FreeBSD vm/usb and give it a run. Their documentation is pretty good and their forums are helpful.
They have all of that. Flatpack is not a thing in Unix and you wouldn’t want it. If you want the terribleness of Flatpack stay on Linux. This post is about self-hosting not Desktop software.
Flatpaks, from the source if available, are excellent: you get the latest versions of the app from the official source, with permissions set for a pretty locked-down sandbox.
What’s not to like, I’m curious?
The storage is cheap these days, if you consider downloads are large. Core apps are robust.
Normally you don't release an app for BSD specifically unless you want to offer a port. In which case software is usually built and if you need containerization you can put it in a jail.
It seems you would do well to install a FreeBSD vm/usb and give it a run. Their documentation is pretty good and their forums are helpful.