The tone and varied assortment of alleged issues makes me feel like he started by deciding that Flatpak was bad, and then found whatever he could to support his view.
I don't have a horse in the flatpak race at all since I don't use it, but the arguments on this website seem strong. I don't really care what someone's motivation for making a point is, I just care whether they're correct or not.
It's technically correct in the same way "ants suck - humans on ants racing is a nightmare" is technically correct. Whether it matters for you depends on your environment / what you want to gain from Flatpak.
If you don't use it (as in don't have a use case you want Flatpak to satisfy), then I think the article is neither right nor wrong.
It’s technically correct in the sense that allowing users to run arbitrary code is a security nightmare. From my own usage and assessment, flatpak seems to be more secure than traditional package managers.
I don't have a horse in the flatpak race at all since I don't use it, but the arguments on this website seem strong. I don't really care what someone's motivation for making a point is, I just care whether they're correct or not.