Flathub is a strange beast. There's no mention of security on their wiki. They stopped publishing minutes (or moved them elsewhere?) in 2017 (https://github.com/flathub/flathub/wiki). They have a buildbot for automated updates from developers, but they accept binaries anyway (e.g. https://github.com/flathub/us.zoom.Zoom/blob/master/us.zoom....), so what's the point? It appears to be a fairly amateur effort, and yet is at the center of the infrastructure Red Hat and Gnome are pushing. I'd love to see some white hat activity targeted at compromising it, to demonstrate the shaky foundations.
But on the other hand, it's nice that I can run Zoom sandboxed (apparently - it's not obvious what the granted permissions are: https://www.flathub.org/apps/details/us.zoom.Zoom). It's nice that Jetbrains and Zoom have a way to publish apps that can run on all distros. It's nice that I could rollback a version of IntelliJ that was buggy with a single snap command that took 5 seconds. The goals are good.
I wish Linus took more of a BDFL approach to the desktop occasionally. Ubuntu & Red Hat need to sit down in a room and have a constructive conversation to converge Snap and Flatpak into something new, deprecating the infrastructure built to date, and fixing some of the glaring problems. There's room for both to make money without further diverging the ecosystem.