For normal desktop users, yeah Debian Stable + Flatpaks is a winning combo for picking the software that you want to be cutting-edge and leaving the rest to rock-solid stability. Normally Linux distros keep a full ecosystem of packages that interop and depend on each other, but solutions like Flatpak have their own little microcosm of dependencies that can be used independently of the host distro. There are also Debian Backports for when you want native Debian packages that are more cutting-edge but still compiled to work with your older base system. Backports are not available for most packages but sometimes the important ones are available, like the Linux kernel itself. You can also try to compile your own backports, but you'll be responsible for updating it.