All of that said, if you are time constrained and really want to look at a single thing, I would go with Flutter. It impressed me when I cranked out a side project with it a year or so ago. Hopefully they continue to put effort towards it.
This was years ago, maybe things have calmed down since then, but Expo always felt like hanging onto the horns of a bull, so long as you didn't fall off it was a fun ride!
Obviously there were a lot of friction when moving out of GetX, but upgrading things have always been easy. Usually at most one day worth of work (worst case). We don't upgrade as soon as a new flutter version is released. We give it a month at least and then upgrade.
During upgrade, most of the problems usually come from 3P dependencies which interact with native such as package info plus. Also, we don't add dependencies unless we really need to. I think we are at ~30 total between all modules.
On the other hand, our react projects are forever in dependency hell. Much larger project, yes but way too many dependencies and too many things break during upgrade.
I think this is the trick. I've worked for a client whose coding standards basically forbade 3rd party clients. Turns out, it often is not needed at all. Do you need to include a library for a bar chart? No, a bar chart is often just a bunch of rectangles and labels.
When you have stupid-simple project setups, you can have huge projects but they'll compile fast and upgrade quickly.
Even Apple can barely get it with SwiftUI being a dumpster fire on macOS.
Don’t get me wrong, I would really love Flutter to be THE solution to the cross platform mobile app problem, but sadly it only gets you 95% there and if you really care about the last 5% you’re out of luck.
I believe it’s good for knocking out an MVP if the mobile app is not critical to your business. I would not choose it otherwise though.