When comparing Proton native vs Flutter, the Slant community recommends Flutter for most people. In the question“What are the best tools for building cross-platform desktop apps with web technologies?” Flutter is ranked 4th while Proton native is ranked 9th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Open source
Pro Uses native tools
Not running a browser to manage the GUI, it uses less resources than the alternatives.
Pro No chromium
Is not based on chromium.
Pro Open source
Pro Great developer tools debug/hotreload/analyser
Pro Based on Dart language
Dart is a Java like language, easy to learn and startup fast for millions of Java developers.
Pro A single codebase for iOS AND Android
Pro Fast
The developer's goal is to allow people to make apps running at 120 FPS.
Cons
Con Not popular
Not being popular as electron js, its development isn't quite at the same pace.
Con No styling
Being based on libui, CSS styling isn't available.
Con Still in development
According to the website, Flutter is still in its early stages of development.
Con Based on Dart language
Dart is a Java like language, easy to learn and startup fast for millions of Java developers. BUT if you have to learn it ... it's a con.
Con Dart is unpopular and never gained serious community traction like Kotlin or Java
Con Does not support 32-bit iOS devices
If you plan on targeting iPhone 5, 5C or earlier, you can forget about Flutter.