Even though pretty old and probably outdated, some points are for sure true. Some apps like Onionshare are horribly outdated, and unless every app has at least one packager responsible for it, best official and paid, its a total mess.
These where not the sources I refer to, and it is pretty complex. Secureblue disables user namespaces and uses bubblewrap-suid for security, but after madaidans statement that would mean a hole in bubblewrap allows the app root privileges.