It’s just, we get so many questions regarding Flatpak from newer users:
Why doesn’t App A tie into App B?
Why doesn’t the program tie into my desktop environment?
How can I install Addons?
Why can’t I access files somewhere
And it’s just not easy. The Apps/Programs are sandboxed and can’t tie into each other unless specifically made for this. Addons need to be put inside of that environment or the program needs to be fitted with some kind of Appstore that incorporates this. You can’t just download an addon from github and drag and drop it like the instruction says. New users blame that on Linux. And you need to understand the additional Flatpak permission system.
In my experience these problems have really increased in the last year or so.
Next thing is, you lose what the distro maintainers do for you. They double check that everything works together well and is tied into your desktop. Breaking changes are postponed until the next major releas of the distro. Since you mentioned Debian, they strip tracking behaviour, and most importanly they fix security issues quickly. Once I read about a severe vulnerability in libpng it’s often already fixed or takes them like one to three days.
Everytime I have a look at ‘flatpak list’ I have like 3 different versions of some runtime installed and it takes half a year until the last flatpak app is updated to the release without that vulnerability. And I get that. Programmers of a project mainly code, and maintenance and packaging the stuff isn’t necessarily top priority on their agenda. But you as a user are exposed for months and I usually expect exploits to appear in the wild after some weeks.
That may be less of a concern if you install OBS via flatpak or a game. But this would be bad if it’s a web-browser or a messenger.
That’s why I usually tell people not to use Flatpak. If you know about the consequences and how to handle the sandboxing and get an addon working, go ahead. Maybe subscribe to a mailing list regarding the security vulnerabilities, because that’s now your job.
For Debian users there are a few alternatives. You could just mix and match software from ‘stable’ and ‘testing’. That is not recommended, but everyone does it. Second thing: Just install Debian testing and you get a rolling distro. That’s what I do and it works great. Well, during the ‘freeze’ for the next version you will experience some delays until they figure out some library updates and dependencies. But that’s alright. [Edit: on second thought: Considering the next comment, maybe I shouldn’t recommend that. It works for me but it definitely has some caveats and you need to understand the consequences I didn’t mention here and be able to fix the occasional hiccup.]