Well I took a look. And followed through the first half of this first Flutter app tutorial to see what it was all about: https://codelabs.developers.google.com/ ... ab-first#0
Seems to me it could be run on Puppy. Maybe via a big addon sfs. Basically it seems it is just a big programming environment so really this thread should be under Programming (albeit assuming anyone provided Flutter installation for Puppy).
I understood the video provided in the above tutorial as far as I could be bothered following it. Basically very object oriented with widgets within widgets and so on. And when you first start creating a new app you have to say what target you want the app to work for, be that Linux, Windows, Desktop, Mac or Web (internet browser) or whatever else it is designed to work for... I guess the Flutter code changes the internal code (not seen by the user/coder) accordingly for whatever target you are building for. But the app code itself can later be easily 'ported' to a different target whilst keeping that same top level code. So, just another app builder. What I don't know is how bulky the resultant apps are and how slow (i.e. how powerful a machine will be sufficient to run them). I bet you the apps will be big!, but I haven't thus far checked any actual example program. I presume they end up compiled - I didn't get that far.
I'm no programmer in that sense per se - object oriented, very abstracted code, that has big framework hiding behind the user coded bits and pieces (widgets and so on and imported Flutter/Dart libs). Being no programmer it bored me to death - but that doesn't mean it will not be useful, maybe even important for young new developers who can be bothered writing apps with such frameworks... How simple it ends up being - your guess is as good as mine, but I suppose pretty simple in the sense that the technical underneath grunt work is all done and provided as part of the framework so the learning process is more to do with learning the Flutter create app technique involving widgets within widgets within widgets. Once app working on any platform (say Linux desktop) easy matter to then re-compile (or whatever) to work on different target (say Android phone). A button can be added and it can be given a simple label widget or instead a whole program can be the widget inside the button widget. I'm yawning now, but maybe someone interested in becoming Flutter expert. But sure, I expect Flutter 'could' be installed on Puppy and apps written with it there - though don't know how heavy and fast or slow such apps will be.
Does it abstract away the problem/issue of whether you are using GTK2,3,4 or whatever? I rather doubt it really - I expect it will be using latest and greatest - though probably there will be a Linux version of Flutter for underlying GTK3 or GTK4, but you'd have to install the correct one anyway, but the written Flutter app will work on either once 're-compiled' or however it is all put together in the end. Main point of it seems to me is not accounting for older technologies (like GTK2 or 3 versus GTK4 and so on), but rather a mechanism to write an app, say using Windows platform as the target, that can later be easily made to work on Linux or Mac or Android, but only if you have the appropriate specified version of GTK or whatever installed - so doesn't address any of the issues Puppy devs face in terms of GTK changes as far as I understand it.