I read that page and there is nonsense included too. Just because I read that page does not make it correct. If you think that AppImages insecure, then you did not understand my point that its not the format thats insecure, but the source where you get the files. Every packaging system is insecure if you get it from bad source.
That’s not even a question. AppImages are fine and not insecure if you download it from a secure place you trust (like your system packages, you trust your distro maintainer fully). Would you trust every distribution maintainer on every distribution? Let’s say a Chinese Linux distribution, that maintains Flatpaks and native packages. Let’s say they are flaky. See? It’s the source you don’t trust, not the file format or packaging system.
Read my replies (just like you said I should read the linked post). And understand the issues.