In over 3 years of daily flatpak use (of multiple apps) I’ve never had a single reliability issue with flatpak, the only ones being caused by me because I was trying out settings in flatseal that the app didn’t like. On the flip side I’ve found native packages to be broken more often than not, with .Deb files sometimes just not working and throwing an error or something. Package managers are better for sure but I’ve had dependency issues that I have never experienced with flatpak.