I’m very new to Flutter and I have to know before learning if Flutter works with Instant App.
Instant apps is currently unavailable on Flutter. There is not really a way to split the functionality, but Flutter also makes your app bigger as you can see in this discussion: https://groups.google.com/d/msg/flutter-dev/JpoMCJsPF-4/lzbUdLigAQAJ
“A trivial Java app does not ship with any graphical engine or widget, everything is provided by the Android Runtime, even most of the standard Java libraries.
A Flutter app has to ship with pretty much everything: engine, widgets, standard libraries, etc …”
I am not completely sure about how much bigger (this example states about 7MB install size), but as Instant Apps have to be below 4MB I don’t think Instant Apps will come to Flutter any time soon if ever.
This year google released Google Play Instant, which basically is a program to test games and application without need to install them on actual device (like Android instant apps). Right now it looks like you have to apply in order get access to the program, but soon should be available for more applications. You can apply here if you want.
This program does not have 4MB limitation any more, but 10MB for the build file size. I guess this is something which could help Flutter applications, because usually they have bigger file size.
In conclusion I would say:
As long as you have android build file (.apk or .aab) and it’s under the upload limitations for Google play store, you can ship it in Google play store as Instant version of your application.