They’re somewhat sandboxed, likely to be up to date, and it behaves similarly across different machines. It’s nice for GUI programs that don’t need access to the wider system, and it won’t mess with anything else that I already have installed. I guess it would have similar pros and cons as containerization with Podman/Docker?

I get the vast majority of my GUI programs from Flathub. I didn’t know there was a controversy with it, other than just wanting a different way of doing things.