Flatpak runtime takes ~300mb + ~300mb for locales (shared between runtimes), with a runtime installed, flatpaks are smaller than .deb counterparts, as .deb still need to install dependencies, that flatpak already has in the runtime, so the size overall is very comparable, the problem is that different apps are on different runtimes due to lack of synchronization in release cycles.
So the summary is:
- under 1gb more space used on end-user machine
- i haven't seen performance difference between .deb and flatpak on 14 years old core2quad + hd6450 + ssd. investigate if on a hdd there is a noticeable difference and how much does it matter. maybe RAM usage will increase, because apps like nautilus aren't flatpaked, so launching nautilus will launch it's gnome dependencies into ram, and then all the other apps will use flatpak version of libraries. a big issue? for sure on Lite. is it worthwhile to have flatpak on core and .deb on lite? probably not, but lite and core use different apps iirc, one is gnome, the other is xfce
- apps add new features and provide fixes that don't get added to .deb unless a whole new Zorin release comes along, so we are stuck with say Calendar 3.36 that on flatpak is v41.2 with added ICS file import.
- removes dependency on given distro packages, making Zorin more flexibile to change distro under the hood
- if users want to install 3rd party flatpak, there is a chance they will not need to download a runtime, as it would already be installed
App candidates for flatpaking:
- gnome calendar, gedit, rhythmbox, evince, clocks, todo, calculator and more.
The problem would be, it'd make sense to help upstream keep them updated, because some gnome flatpaks are at v41, and some still use v40 etc. which requires 300mb for each differing runtime needed, ideally there would be only one runtime.